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-rw-r--r--synapse/__init__.py2
-rw-r--r--synapse/api/errors.py1
-rw-r--r--synapse/config/consent_config.py19
-rw-r--r--synapse/config/server_notices_config.py15
-rw-r--r--synapse/events/utils.py4
-rw-r--r--synapse/events/validator.py6
-rw-r--r--synapse/groups/groups_server.py4
-rw-r--r--synapse/handlers/deactivate_account.py6
-rw-r--r--synapse/handlers/device.py14
-rw-r--r--synapse/handlers/e2e_keys.py13
-rw-r--r--synapse/handlers/federation.py50
-rw-r--r--synapse/handlers/groups_local.py3
-rw-r--r--synapse/handlers/message.py18
-rw-r--r--synapse/handlers/presence.py15
-rw-r--r--synapse/handlers/room_member.py23
-rw-r--r--synapse/handlers/sync.py14
-rw-r--r--synapse/handlers/user_directory.py10
-rw-r--r--synapse/http/matrixfederationclient.py8
-rw-r--r--synapse/http/site.py2
-rw-r--r--synapse/push/bulk_push_rule_evaluator.py13
-rw-r--r--synapse/push/push_rule_evaluator.py4
-rw-r--r--synapse/replication/tcp/protocol.py14
-rw-r--r--synapse/replication/tcp/resource.py3
-rw-r--r--synapse/rest/client/v1/presence.py8
-rw-r--r--synapse/rest/media/v1/media_repository.py3
-rw-r--r--synapse/rest/media/v1/preview_url_resource.py8
-rw-r--r--synapse/server_notices/consent_server_notices.py46
-rw-r--r--synapse/server_notices/server_notices_manager.py23
-rw-r--r--synapse/server_notices/worker_server_notices_sender.py2
-rw-r--r--synapse/state.py48
-rw-r--r--synapse/storage/_base.py47
-rw-r--r--synapse/storage/client_ips.py6
-rw-r--r--synapse/storage/devices.py9
-rw-r--r--synapse/storage/end_to_end_keys.py6
-rw-r--r--synapse/storage/event_push_actions.py4
-rw-r--r--synapse/storage/events_worker.py2
-rw-r--r--synapse/storage/filtering.py2
-rw-r--r--synapse/storage/keys.py2
-rw-r--r--synapse/storage/roommember.py10
-rw-r--r--synapse/storage/stream.py15
-rw-r--r--synapse/util/__init__.py18
-rw-r--r--synapse/util/caches/__init__.py7
42 files changed, 353 insertions, 174 deletions
diff --git a/synapse/__init__.py b/synapse/__init__.py
index b11a1d3ea3..5bada5e290 100644
--- a/synapse/__init__.py
+++ b/synapse/__init__.py
@@ -16,4 +16,4 @@
 """ This is a reference implementation of a Matrix home server.
 """
 
-__version__ = "0.29.1"
+__version__ = "0.30.0"
diff --git a/synapse/api/errors.py b/synapse/api/errors.py
index aca804280c..e6ad3768f0 100644
--- a/synapse/api/errors.py
+++ b/synapse/api/errors.py
@@ -53,6 +53,7 @@ class Codes(object):
     INVALID_USERNAME = "M_INVALID_USERNAME"
     SERVER_NOT_TRUSTED = "M_SERVER_NOT_TRUSTED"
     CONSENT_NOT_GIVEN = "M_CONSENT_NOT_GIVEN"
+    CANNOT_LEAVE_SERVER_NOTICE_ROOM = "M_CANNOT_LEAVE_SERVER_NOTICE_ROOM"
 
 
 class CodeMessageException(RuntimeError):
diff --git a/synapse/config/consent_config.py b/synapse/config/consent_config.py
index 44c4711e6c..8f6ed73328 100644
--- a/synapse/config/consent_config.py
+++ b/synapse/config/consent_config.py
@@ -32,7 +32,8 @@ DEFAULT_CONFIG = """\
 #
 # 'server_notice_content', if enabled, will send a user a "Server Notice"
 # asking them to consent to the privacy policy. The 'server_notices' section
-# must also be configured for this to work.
+# must also be configured for this to work. Notices will *not* be sent to
+# guest users unless 'send_server_notice_to_guests' is set to true.
 #
 # 'block_events_error', if set, will block any attempts to send events
 # until the user consents to the privacy policy. The value of the setting is
@@ -43,10 +44,14 @@ DEFAULT_CONFIG = """\
 #   version: 1.0
 #   server_notice_content:
 #     msgtype: m.text
-#     body: |
-#       Pls do consent kthx
-#   block_events_error: |
-#     You can't send any messages until you consent to the privacy policy.
+#     body: >-
+#       To continue using this homeserver you must review and agree to the
+#       terms and conditions at %(consent_uri)s
+#   send_server_notice_to_guests: True
+#   block_events_error: >-
+#     To continue using this homeserver you must review and agree to the
+#     terms and conditions at %(consent_uri)s
+#
 """
 
 
@@ -57,6 +62,7 @@ class ConsentConfig(Config):
         self.user_consent_version = None
         self.user_consent_template_dir = None
         self.user_consent_server_notice_content = None
+        self.user_consent_server_notice_to_guests = False
         self.block_events_without_consent_error = None
 
     def read_config(self, config):
@@ -71,6 +77,9 @@ class ConsentConfig(Config):
         self.block_events_without_consent_error = consent_config.get(
             "block_events_error",
         )
+        self.user_consent_server_notice_to_guests = bool(consent_config.get(
+            "send_server_notice_to_guests", False,
+        ))
 
     def default_config(self, **kwargs):
         return DEFAULT_CONFIG
diff --git a/synapse/config/server_notices_config.py b/synapse/config/server_notices_config.py
index ccef8d2ec5..be1d1f762c 100644
--- a/synapse/config/server_notices_config.py
+++ b/synapse/config/server_notices_config.py
@@ -26,12 +26,13 @@ DEFAULT_CONFIG = """\
 # setting, which defines the id of the user which will be used to send the
 # notices.
 #
-# It's also possible to override the room name, or the display name of the
-# "notices" user.
+# It's also possible to override the room name, the display name of the
+# "notices" user, and the avatar for the user.
 #
 # server_notices:
 #   system_mxid_localpart: notices
 #   system_mxid_display_name: "Server Notices"
+#   system_mxid_avatar_url: "mxc://server.com/oumMVlgDnLYFaPVkExemNVVZ"
 #   room_name: "Server Notices"
 """
 
@@ -48,6 +49,10 @@ class ServerNoticesConfig(Config):
             The display name to use for the server notices user.
             None if server notices are not enabled.
 
+        server_notices_mxid_avatar_url (str|None):
+            The display name to use for the server notices user.
+            None if server notices are not enabled.
+
         server_notices_room_name (str|None):
             The name to use for the server notices room.
             None if server notices are not enabled.
@@ -56,6 +61,7 @@ class ServerNoticesConfig(Config):
         super(ServerNoticesConfig, self).__init__()
         self.server_notices_mxid = None
         self.server_notices_mxid_display_name = None
+        self.server_notices_mxid_avatar_url = None
         self.server_notices_room_name = None
 
     def read_config(self, config):
@@ -68,7 +74,10 @@ class ServerNoticesConfig(Config):
             mxid_localpart, self.server_name,
         ).to_string()
         self.server_notices_mxid_display_name = c.get(
-            'system_mxid_display_name', 'Server Notices',
+            'system_mxid_display_name', None,
+        )
+        self.server_notices_mxid_avatar_url = c.get(
+            'system_mxid_avatar_url', None,
         )
         # todo: i18n
         self.server_notices_room_name = c.get('room_name', "Server Notices")
diff --git a/synapse/events/utils.py b/synapse/events/utils.py
index 824f4a42e3..29ae086786 100644
--- a/synapse/events/utils.py
+++ b/synapse/events/utils.py
@@ -20,6 +20,8 @@ from frozendict import frozendict
 
 import re
 
+from six import string_types
+
 # Split strings on "." but not "\." This uses a negative lookbehind assertion for '\'
 # (?<!stuff) matches if the current position in the string is not preceded
 # by a match for 'stuff'.
@@ -277,7 +279,7 @@ def serialize_event(e, time_now_ms, as_client_event=True,
 
     if only_event_fields:
         if (not isinstance(only_event_fields, list) or
-                not all(isinstance(f, basestring) for f in only_event_fields)):
+                not all(isinstance(f, string_types) for f in only_event_fields)):
             raise TypeError("only_event_fields must be a list of strings")
         d = only_fields(d, only_event_fields)
 
diff --git a/synapse/events/validator.py b/synapse/events/validator.py
index 2f4c8a1018..e0e5bf818c 100644
--- a/synapse/events/validator.py
+++ b/synapse/events/validator.py
@@ -17,6 +17,8 @@ from synapse.types import EventID, RoomID, UserID
 from synapse.api.errors import SynapseError
 from synapse.api.constants import EventTypes, Membership
 
+from six import string_types
+
 
 class EventValidator(object):
 
@@ -49,7 +51,7 @@ class EventValidator(object):
             strings.append("state_key")
 
         for s in strings:
-            if not isinstance(getattr(event, s), basestring):
+            if not isinstance(getattr(event, s), string_types):
                 raise SynapseError(400, "Not '%s' a string type" % (s,))
 
         if event.type == EventTypes.Member:
@@ -88,5 +90,5 @@ class EventValidator(object):
         for s in keys:
             if s not in d:
                 raise SynapseError(400, "'%s' not in content" % (s,))
-            if not isinstance(d[s], basestring):
+            if not isinstance(d[s], string_types):
                 raise SynapseError(400, "Not '%s' a string type" % (s,))
diff --git a/synapse/groups/groups_server.py b/synapse/groups/groups_server.py
index 2d95b04e0c..62d20ad130 100644
--- a/synapse/groups/groups_server.py
+++ b/synapse/groups/groups_server.py
@@ -20,6 +20,8 @@ from synapse.api.errors import SynapseError
 from synapse.types import GroupID, RoomID, UserID, get_domain_from_id
 from twisted.internet import defer
 
+from six import string_types
+
 logger = logging.getLogger(__name__)
 
 
@@ -431,7 +433,7 @@ class GroupsServerHandler(object):
                         "long_description"):
             if keyname in content:
                 value = content[keyname]
-                if not isinstance(value, basestring):
+                if not isinstance(value, string_types):
                     raise SynapseError(400, "%r value is not a string" % (keyname,))
                 profile[keyname] = value
 
diff --git a/synapse/handlers/deactivate_account.py b/synapse/handlers/deactivate_account.py
index 4eb18775e8..c5e92f6214 100644
--- a/synapse/handlers/deactivate_account.py
+++ b/synapse/handlers/deactivate_account.py
@@ -30,6 +30,7 @@ class DeactivateAccountHandler(BaseHandler):
         self._auth_handler = hs.get_auth_handler()
         self._device_handler = hs.get_device_handler()
         self._room_member_handler = hs.get_room_member_handler()
+        self.user_directory_handler = hs.get_user_directory_handler()
 
         # Flag that indicates whether the process to part users from rooms is running
         self._user_parter_running = False
@@ -61,10 +62,13 @@ class DeactivateAccountHandler(BaseHandler):
         yield self.store.user_delete_threepids(user_id)
         yield self.store.user_set_password_hash(user_id, None)
 
-        # Add the user to a table of users penpding deactivation (ie.
+        # Add the user to a table of users pending deactivation (ie.
         # removal from all the rooms they're a member of)
         yield self.store.add_user_pending_deactivation(user_id)
 
+        # delete from user directory
+        yield self.user_directory_handler.handle_user_deactivated(user_id)
+
         # Now start the process that goes through that list and
         # parts users from rooms (if it isn't already running)
         self._start_user_parting()
diff --git a/synapse/handlers/device.py b/synapse/handlers/device.py
index f7457a7082..31bd0e60c6 100644
--- a/synapse/handlers/device.py
+++ b/synapse/handlers/device.py
@@ -26,6 +26,8 @@ from ._base import BaseHandler
 
 import logging
 
+from six import itervalues, iteritems
+
 logger = logging.getLogger(__name__)
 
 
@@ -318,7 +320,7 @@ class DeviceHandler(BaseHandler):
             # The user may have left the room
             # TODO: Check if they actually did or if we were just invited.
             if room_id not in room_ids:
-                for key, event_id in current_state_ids.iteritems():
+                for key, event_id in iteritems(current_state_ids):
                     etype, state_key = key
                     if etype != EventTypes.Member:
                         continue
@@ -338,7 +340,7 @@ class DeviceHandler(BaseHandler):
             # special-case for an empty prev state: include all members
             # in the changed list
             if not event_ids:
-                for key, event_id in current_state_ids.iteritems():
+                for key, event_id in iteritems(current_state_ids):
                     etype, state_key = key
                     if etype != EventTypes.Member:
                         continue
@@ -354,10 +356,10 @@ class DeviceHandler(BaseHandler):
 
             # Check if we've joined the room? If so we just blindly add all the users to
             # the "possibly changed" users.
-            for state_dict in prev_state_ids.itervalues():
+            for state_dict in itervalues(prev_state_ids):
                 member_event = state_dict.get((EventTypes.Member, user_id), None)
                 if not member_event or member_event != current_member_id:
-                    for key, event_id in current_state_ids.iteritems():
+                    for key, event_id in iteritems(current_state_ids):
                         etype, state_key = key
                         if etype != EventTypes.Member:
                             continue
@@ -367,14 +369,14 @@ class DeviceHandler(BaseHandler):
             # If there has been any change in membership, include them in the
             # possibly changed list. We'll check if they are joined below,
             # and we're not toooo worried about spuriously adding users.
-            for key, event_id in current_state_ids.iteritems():
+            for key, event_id in iteritems(current_state_ids):
                 etype, state_key = key
                 if etype != EventTypes.Member:
                     continue
 
                 # check if this member has changed since any of the extremities
                 # at the stream_ordering, and add them to the list if so.
-                for state_dict in prev_state_ids.itervalues():
+                for state_dict in itervalues(prev_state_ids):
                     prev_event_id = state_dict.get(key, None)
                     if not prev_event_id or prev_event_id != event_id:
                         if state_key != user_id:
diff --git a/synapse/handlers/e2e_keys.py b/synapse/handlers/e2e_keys.py
index 25aec624af..8a2d177539 100644
--- a/synapse/handlers/e2e_keys.py
+++ b/synapse/handlers/e2e_keys.py
@@ -19,6 +19,7 @@ import logging
 
 from canonicaljson import encode_canonical_json
 from twisted.internet import defer
+from six import iteritems
 
 from synapse.api.errors import (
     SynapseError, CodeMessageException, FederationDeniedError,
@@ -92,7 +93,7 @@ class E2eKeysHandler(object):
         remote_queries_not_in_cache = {}
         if remote_queries:
             query_list = []
-            for user_id, device_ids in remote_queries.iteritems():
+            for user_id, device_ids in iteritems(remote_queries):
                 if device_ids:
                     query_list.extend((user_id, device_id) for device_id in device_ids)
                 else:
@@ -103,9 +104,9 @@ class E2eKeysHandler(object):
                     query_list
                 )
             )
-            for user_id, devices in remote_results.iteritems():
+            for user_id, devices in iteritems(remote_results):
                 user_devices = results.setdefault(user_id, {})
-                for device_id, device in devices.iteritems():
+                for device_id, device in iteritems(devices):
                     keys = device.get("keys", None)
                     device_display_name = device.get("device_display_name", None)
                     if keys:
@@ -250,9 +251,9 @@ class E2eKeysHandler(object):
             "Claimed one-time-keys: %s",
             ",".join((
                 "%s for %s:%s" % (key_id, user_id, device_id)
-                for user_id, user_keys in json_result.iteritems()
-                for device_id, device_keys in user_keys.iteritems()
-                for key_id, _ in device_keys.iteritems()
+                for user_id, user_keys in iteritems(json_result)
+                for device_id, device_keys in iteritems(user_keys)
+                for key_id, _ in iteritems(device_keys)
             )),
         )
 
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index ba3ede8024..87c0615820 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -24,6 +24,7 @@ from signedjson.key import decode_verify_key_bytes
 from signedjson.sign import verify_signed_json
 import six
 from six.moves import http_client
+from six import iteritems
 from twisted.internet import defer
 from unpaddedbase64 import decode_base64
 
@@ -479,18 +480,18 @@ class FederationHandler(BaseHandler):
         # to get all state ids that we're interested in.
         event_map = yield self.store.get_events([
             e_id
-            for key_to_eid in event_to_state_ids.values()
-            for key, e_id in key_to_eid.items()
+            for key_to_eid in event_to_state_ids.itervalues()
+            for key, e_id in key_to_eid.iteritems()
             if key[0] != EventTypes.Member or check_match(key[1])
         ])
 
         event_to_state = {
             e_id: {
                 key: event_map[inner_e_id]
-                for key, inner_e_id in key_to_eid.items()
+                for key, inner_e_id in key_to_eid.iteritems()
                 if inner_e_id in event_map
             }
-            for e_id, key_to_eid in event_to_state_ids.items()
+            for e_id, key_to_eid in event_to_state_ids.iteritems()
         }
 
         def redact_disallowed(event, state):
@@ -505,7 +506,7 @@ class FederationHandler(BaseHandler):
                     # membership states for the requesting server to determine
                     # if the server is either in the room or has been invited
                     # into the room.
-                    for ev in state.values():
+                    for ev in state.itervalues():
                         if ev.type != EventTypes.Member:
                             continue
                         try:
@@ -751,9 +752,19 @@ class FederationHandler(BaseHandler):
         curr_state = yield self.state_handler.get_current_state(room_id)
 
         def get_domains_from_state(state):
+            """Get joined domains from state
+
+            Args:
+                state (dict[tuple, FrozenEvent]): State map from type/state
+                    key to event.
+
+            Returns:
+                list[tuple[str, int]]: Returns a list of servers with the
+                lowest depth of their joins. Sorted by lowest depth first.
+            """
             joined_users = [
                 (state_key, int(event.depth))
-                for (e_type, state_key), event in state.items()
+                for (e_type, state_key), event in state.iteritems()
                 if e_type == EventTypes.Member
                 and event.membership == Membership.JOIN
             ]
@@ -770,7 +781,7 @@ class FederationHandler(BaseHandler):
                 except Exception:
                     pass
 
-            return sorted(joined_domains.items(), key=lambda d: d[1])
+            return sorted(joined_domains.iteritems(), key=lambda d: d[1])
 
         curr_domains = get_domains_from_state(curr_state)
 
@@ -787,7 +798,7 @@ class FederationHandler(BaseHandler):
                     yield self.backfill(
                         dom, room_id,
                         limit=100,
-                        extremities=[e for e in extremities.keys()]
+                        extremities=extremities,
                     )
                     # If this succeeded then we probably already have the
                     # appropriate stuff.
@@ -833,7 +844,7 @@ class FederationHandler(BaseHandler):
         tried_domains = set(likely_domains)
         tried_domains.add(self.server_name)
 
-        event_ids = list(extremities.keys())
+        event_ids = list(extremities.iterkeys())
 
         logger.debug("calling resolve_state_groups in _maybe_backfill")
         resolve = logcontext.preserve_fn(
@@ -843,31 +854,34 @@ class FederationHandler(BaseHandler):
             [resolve(room_id, [e]) for e in event_ids],
             consumeErrors=True,
         ))
+
+        # dict[str, dict[tuple, str]], a map from event_id to state map of
+        # event_ids.
         states = dict(zip(event_ids, [s.state for s in states]))
 
         state_map = yield self.store.get_events(
-            [e_id for ids in states.values() for e_id in ids],
+            [e_id for ids in states.itervalues() for e_id in ids.itervalues()],
             get_prev_content=False
         )
         states = {
             key: {
                 k: state_map[e_id]
-                for k, e_id in state_dict.items()
+                for k, e_id in state_dict.iteritems()
                 if e_id in state_map
-            } for key, state_dict in states.items()
+            } for key, state_dict in states.iteritems()
         }
 
         for e_id, _ in sorted_extremeties_tuple:
             likely_domains = get_domains_from_state(states[e_id])
 
             success = yield try_backfill([
-                dom for dom in likely_domains
+                dom for dom, _ in likely_domains
                 if dom not in tried_domains
             ])
             if success:
                 defer.returnValue(True)
 
-            tried_domains.update(likely_domains)
+            tried_domains.update(dom for dom, _ in likely_domains)
 
         defer.returnValue(False)
 
@@ -1375,7 +1389,7 @@ class FederationHandler(BaseHandler):
         )
 
         if state_groups:
-            _, state = state_groups.items().pop()
+            _, state = list(iteritems(state_groups)).pop()
             results = {
                 (e.type, e.state_key): e for e in state
             }
@@ -2021,7 +2035,7 @@ class FederationHandler(BaseHandler):
                 this will not be included in the current_state in the context.
         """
         state_updates = {
-            k: a.event_id for k, a in auth_events.iteritems()
+            k: a.event_id for k, a in iteritems(auth_events)
             if k != event_key
         }
         context.current_state_ids = dict(context.current_state_ids)
@@ -2031,7 +2045,7 @@ class FederationHandler(BaseHandler):
             context.delta_ids.update(state_updates)
         context.prev_state_ids = dict(context.prev_state_ids)
         context.prev_state_ids.update({
-            k: a.event_id for k, a in auth_events.iteritems()
+            k: a.event_id for k, a in iteritems(auth_events)
         })
         context.state_group = yield self.store.store_state_group(
             event.event_id,
@@ -2083,7 +2097,7 @@ class FederationHandler(BaseHandler):
 
         def get_next(it, opt=None):
             try:
-                return it.next()
+                return next(it)
             except Exception:
                 return opt
 
diff --git a/synapse/handlers/groups_local.py b/synapse/handlers/groups_local.py
index 977993e7d4..dcae083734 100644
--- a/synapse/handlers/groups_local.py
+++ b/synapse/handlers/groups_local.py
@@ -15,6 +15,7 @@
 # limitations under the License.
 
 from twisted.internet import defer
+from six import iteritems
 
 from synapse.api.errors import SynapseError
 from synapse.types import get_domain_from_id
@@ -449,7 +450,7 @@ class GroupsLocalHandler(object):
 
         results = {}
         failed_results = []
-        for destination, dest_user_ids in destinations.iteritems():
+        for destination, dest_user_ids in iteritems(destinations):
             try:
                 r = yield self.transport_client.bulk_get_publicised_groups(
                     destination, list(dest_user_ids),
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index c3adbc6c95..81cff0870e 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -19,6 +19,7 @@ import sys
 
 from canonicaljson import encode_canonical_json
 import six
+from six import string_types, itervalues, iteritems
 from twisted.internet import defer, reactor
 from twisted.internet.defer import succeed
 from twisted.python.failure import Failure
@@ -402,7 +403,7 @@ class MessageHandler(BaseHandler):
                 "avatar_url": profile.avatar_url,
                 "display_name": profile.display_name,
             }
-            for user_id, profile in users_with_profile.iteritems()
+            for user_id, profile in iteritems(users_with_profile)
         })
 
 
@@ -574,9 +575,14 @@ class EventCreationHandler(object):
         if u["consent_version"] == self.config.user_consent_version:
             return
 
-        consent_uri = self._consent_uri_builder.build_user_consent_uri(user_id)
+        consent_uri = self._consent_uri_builder.build_user_consent_uri(
+            requester.user.localpart,
+        )
+        msg = self.config.block_events_without_consent_error % {
+            'consent_uri': consent_uri,
+        }
         raise ConsentNotGivenError(
-            msg=self.config.block_events_without_consent_error,
+            msg=msg,
             consent_uri=consent_uri,
         )
 
@@ -662,7 +668,7 @@ class EventCreationHandler(object):
 
             spam_error = self.spam_checker.check_event_for_spam(event)
             if spam_error:
-                if not isinstance(spam_error, basestring):
+                if not isinstance(spam_error, string_types):
                     spam_error = "Spam is not permitted here"
                 raise SynapseError(
                     403, spam_error, Codes.FORBIDDEN
@@ -876,7 +882,7 @@ class EventCreationHandler(object):
 
                 state_to_include_ids = [
                     e_id
-                    for k, e_id in context.current_state_ids.iteritems()
+                    for k, e_id in iteritems(context.current_state_ids)
                     if k[0] in self.hs.config.room_invite_state_types
                     or k == (EventTypes.Member, event.sender)
                 ]
@@ -890,7 +896,7 @@ class EventCreationHandler(object):
                         "content": e.content,
                         "sender": e.sender,
                     }
-                    for e in state_to_include.itervalues()
+                    for e in itervalues(state_to_include)
                 ]
 
                 invitee = UserID.from_string(event.state_key)
diff --git a/synapse/handlers/presence.py b/synapse/handlers/presence.py
index 12939aa507..26fc0d3ec7 100644
--- a/synapse/handlers/presence.py
+++ b/synapse/handlers/presence.py
@@ -25,6 +25,8 @@ The methods that define policy are:
 from twisted.internet import defer, reactor
 from contextlib import contextmanager
 
+from six import itervalues, iteritems
+
 from synapse.api.errors import SynapseError
 from synapse.api.constants import PresenceState
 from synapse.storage.presence import UserPresenceState
@@ -42,7 +44,6 @@ import logging
 
 from prometheus_client import Counter
 
-
 logger = logging.getLogger(__name__)
 
 
@@ -535,7 +536,7 @@ class PresenceHandler(object):
                 prev_state.copy_and_replace(
                     last_user_sync_ts=time_now_ms,
                 )
-                for prev_state in prev_states.itervalues()
+                for prev_state in itervalues(prev_states)
             ])
             self.external_process_last_updated_ms.pop(process_id, None)
 
@@ -558,14 +559,14 @@ class PresenceHandler(object):
             for user_id in user_ids
         }
 
-        missing = [user_id for user_id, state in states.iteritems() if not state]
+        missing = [user_id for user_id, state in iteritems(states) if not state]
         if missing:
             # There are things not in our in memory cache. Lets pull them out of
             # the database.
             res = yield self.store.get_presence_for_users(missing)
             states.update(res)
 
-            missing = [user_id for user_id, state in states.iteritems() if not state]
+            missing = [user_id for user_id, state in iteritems(states) if not state]
             if missing:
                 new = {
                     user_id: UserPresenceState.default(user_id)
@@ -1053,7 +1054,7 @@ class PresenceEventSource(object):
             defer.returnValue((updates.values(), max_token))
         else:
             defer.returnValue(([
-                s for s in updates.itervalues()
+                s for s in itervalues(updates)
                 if s.state != PresenceState.OFFLINE
             ], max_token))
 
@@ -1310,11 +1311,11 @@ def get_interested_remotes(store, states, state_handler):
     # hosts in those rooms.
     room_ids_to_states, users_to_states = yield get_interested_parties(store, states)
 
-    for room_id, states in room_ids_to_states.iteritems():
+    for room_id, states in iteritems(room_ids_to_states):
         hosts = yield state_handler.get_current_hosts_in_room(room_id)
         hosts_and_states.append((hosts, states))
 
-    for user_id, states in users_to_states.iteritems():
+    for user_id, states in iteritems(users_to_states):
         host = get_domain_from_id(user_id)
         hosts_and_states.append(([host], states))
 
diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py
index 5263f09aaa..f930e939e8 100644
--- a/synapse/handlers/room_member.py
+++ b/synapse/handlers/room_member.py
@@ -298,15 +298,6 @@ class RoomMemberHandler(object):
             is_blocked = yield self.store.is_room_blocked(room_id)
             if is_blocked:
                 raise SynapseError(403, "This room has been blocked on this server")
-        else:
-            # we don't allow people to reject invites to, or leave, the
-            # server notice room.
-            is_blocked = yield self._is_server_notice_room(room_id)
-            if is_blocked:
-                raise SynapseError(
-                    http_client.FORBIDDEN,
-                    "You cannot leave this room",
-                )
 
         if effective_membership_state == Membership.INVITE:
             # block any attempts to invite the server notices mxid
@@ -382,6 +373,20 @@ class RoomMemberHandler(object):
                 if same_sender and same_membership and same_content:
                     defer.returnValue(old_state)
 
+            # we don't allow people to reject invites to the server notice
+            # room, but they can leave it once they are joined.
+            if (
+                old_membership == Membership.INVITE and
+                effective_membership_state == Membership.LEAVE
+            ):
+                is_blocked = yield self._is_server_notice_room(room_id)
+                if is_blocked:
+                    raise SynapseError(
+                        http_client.FORBIDDEN,
+                        "You cannot reject this invite",
+                        errcode=Codes.CANNOT_LEAVE_SERVER_NOTICE_ROOM,
+                    )
+
         is_host_in_room = yield self._is_host_in_room(current_state_ids)
 
         if effective_membership_state == Membership.JOIN:
diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py
index 263e42dded..d0c99c35e3 100644
--- a/synapse/handlers/sync.py
+++ b/synapse/handlers/sync.py
@@ -28,6 +28,8 @@ import collections
 import logging
 import itertools
 
+from six import itervalues, iteritems
+
 logger = logging.getLogger(__name__)
 
 
@@ -275,7 +277,7 @@ class SyncHandler(object):
                 # result returned by the event source is poor form (it might cache
                 # the object)
                 room_id = event["room_id"]
-                event_copy = {k: v for (k, v) in event.iteritems()
+                event_copy = {k: v for (k, v) in iteritems(event)
                               if k != "room_id"}
                 ephemeral_by_room.setdefault(room_id, []).append(event_copy)
 
@@ -294,7 +296,7 @@ class SyncHandler(object):
             for event in receipts:
                 room_id = event["room_id"]
                 # exclude room id, as above
-                event_copy = {k: v for (k, v) in event.iteritems()
+                event_copy = {k: v for (k, v) in iteritems(event)
                               if k != "room_id"}
                 ephemeral_by_room.setdefault(room_id, []).append(event_copy)
 
@@ -325,7 +327,7 @@ class SyncHandler(object):
                 current_state_ids = frozenset()
                 if any(e.is_state() for e in recents):
                     current_state_ids = yield self.state.get_current_state_ids(room_id)
-                    current_state_ids = frozenset(current_state_ids.itervalues())
+                    current_state_ids = frozenset(itervalues(current_state_ids))
 
                 recents = yield filter_events_for_client(
                     self.store,
@@ -382,7 +384,7 @@ class SyncHandler(object):
                 current_state_ids = frozenset()
                 if any(e.is_state() for e in loaded_recents):
                     current_state_ids = yield self.state.get_current_state_ids(room_id)
-                    current_state_ids = frozenset(current_state_ids.itervalues())
+                    current_state_ids = frozenset(itervalues(current_state_ids))
 
                 loaded_recents = yield filter_events_for_client(
                     self.store,
@@ -984,7 +986,7 @@ class SyncHandler(object):
         if since_token:
             for joined_sync in sync_result_builder.joined:
                 it = itertools.chain(
-                    joined_sync.timeline.events, joined_sync.state.itervalues()
+                    joined_sync.timeline.events, itervalues(joined_sync.state)
                 )
                 for event in it:
                     if event.type == EventTypes.Member:
@@ -1062,7 +1064,7 @@ class SyncHandler(object):
         newly_left_rooms = []
         room_entries = []
         invited = []
-        for room_id, events in mem_change_events_by_room_id.iteritems():
+        for room_id, events in iteritems(mem_change_events_by_room_id):
             non_joins = [e for e in events if e.membership != Membership.JOIN]
             has_join = len(non_joins) != len(events)
 
diff --git a/synapse/handlers/user_directory.py b/synapse/handlers/user_directory.py
index 714f0195c8..a39f0f7343 100644
--- a/synapse/handlers/user_directory.py
+++ b/synapse/handlers/user_directory.py
@@ -22,6 +22,7 @@ from synapse.util.metrics import Measure
 from synapse.util.async import sleep
 from synapse.types import get_localpart_from_id
 
+from six import iteritems
 
 logger = logging.getLogger(__name__)
 
@@ -123,6 +124,13 @@ class UserDirectoryHandler(object):
         )
 
     @defer.inlineCallbacks
+    def handle_user_deactivated(self, user_id):
+        """Called when a user ID is deactivated
+        """
+        yield self.store.remove_from_user_dir(user_id)
+        yield self.store.remove_from_user_in_public_room(user_id)
+
+    @defer.inlineCallbacks
     def _unsafe_process(self):
         # If self.pos is None then means we haven't fetched it from DB
         if self.pos is None:
@@ -403,7 +411,7 @@ class UserDirectoryHandler(object):
 
         if change:
             users_with_profile = yield self.state.get_current_user_in_room(room_id)
-            for user_id, profile in users_with_profile.iteritems():
+            for user_id, profile in iteritems(users_with_profile):
                 yield self._handle_new_user(room_id, user_id, profile)
         else:
             users = yield self.store.get_users_in_public_due_to_room(room_id)
diff --git a/synapse/http/matrixfederationclient.py b/synapse/http/matrixfederationclient.py
index 77eaa06a1a..821aed362b 100644
--- a/synapse/http/matrixfederationclient.py
+++ b/synapse/http/matrixfederationclient.py
@@ -42,6 +42,8 @@ import random
 import sys
 import urllib
 from six.moves.urllib import parse as urlparse
+from six import string_types
+
 
 from prometheus_client import Counter
 
@@ -549,7 +551,7 @@ class MatrixFederationHttpClient(object):
 
         encoded_args = {}
         for k, vs in args.items():
-            if isinstance(vs, basestring):
+            if isinstance(vs, string_types):
                 vs = [vs]
             encoded_args[k] = [v.encode("UTF-8") for v in vs]
 
@@ -664,7 +666,7 @@ def check_content_type_is_json(headers):
         RuntimeError if the
 
     """
-    c_type = headers.getRawHeaders("Content-Type")
+    c_type = headers.getRawHeaders(b"Content-Type")
     if c_type is None:
         raise RuntimeError(
             "No Content-Type header"
@@ -681,7 +683,7 @@ def check_content_type_is_json(headers):
 def encode_query_args(args):
     encoded_args = {}
     for k, vs in args.items():
-        if isinstance(vs, basestring):
+        if isinstance(vs, string_types):
             vs = [vs]
         encoded_args[k] = [v.encode("UTF-8") for v in vs]
 
diff --git a/synapse/http/site.py b/synapse/http/site.py
index b608504225..23c1b76922 100644
--- a/synapse/http/site.py
+++ b/synapse/http/site.py
@@ -56,7 +56,7 @@ class SynapseRequest(Request):
 
     def __repr__(self):
         # We overwrite this so that we don't log ``access_token``
-        return '<%s at 0x%x method=%s uri=%s clientproto=%s site=%s>' % (
+        return '<%s at 0x%x method=%r uri=%r clientproto=%r site=%r>' % (
             self.__class__.__name__,
             id(self),
             self.method,
diff --git a/synapse/push/bulk_push_rule_evaluator.py b/synapse/push/bulk_push_rule_evaluator.py
index da1cde417f..a5cab1f043 100644
--- a/synapse/push/bulk_push_rule_evaluator.py
+++ b/synapse/push/bulk_push_rule_evaluator.py
@@ -29,6 +29,7 @@ from synapse.state import POWER_KEY
 
 from collections import namedtuple
 from prometheus_client import Counter
+from six import itervalues, iteritems
 
 logger = logging.getLogger(__name__)
 
@@ -122,7 +123,7 @@ class BulkPushRuleEvaluator(object):
             )
             auth_events = yield self.store.get_events(auth_events_ids)
             auth_events = {
-                (e.type, e.state_key): e for e in auth_events.itervalues()
+                (e.type, e.state_key): e for e in itervalues(auth_events)
             }
 
         sender_level = get_user_power_level(event.sender, auth_events)
@@ -156,7 +157,7 @@ class BulkPushRuleEvaluator(object):
 
         condition_cache = {}
 
-        for uid, rules in rules_by_user.iteritems():
+        for uid, rules in iteritems(rules_by_user):
             if event.sender == uid:
                 continue
 
@@ -402,7 +403,7 @@ class RulesForRoom(object):
         # If the event is a join event then it will be in current state evnts
         # map but not in the DB, so we have to explicitly insert it.
         if event.type == EventTypes.Member:
-            for event_id in member_event_ids.itervalues():
+            for event_id in itervalues(member_event_ids):
                 if event_id == event.event_id:
                     members[event_id] = (event.state_key, event.membership)
 
@@ -410,7 +411,7 @@ class RulesForRoom(object):
             logger.debug("Found members %r: %r", self.room_id, members.values())
 
         interested_in_user_ids = set(
-            user_id for user_id, membership in members.itervalues()
+            user_id for user_id, membership in itervalues(members)
             if membership == Membership.JOIN
         )
 
@@ -422,7 +423,7 @@ class RulesForRoom(object):
         )
 
         user_ids = set(
-            uid for uid, have_pusher in if_users_with_pushers.iteritems() if have_pusher
+            uid for uid, have_pusher in iteritems(if_users_with_pushers) if have_pusher
         )
 
         logger.debug("With pushers: %r", user_ids)
@@ -443,7 +444,7 @@ class RulesForRoom(object):
         )
 
         ret_rules_by_user.update(
-            item for item in rules_by_user.iteritems() if item[0] is not None
+            item for item in iteritems(rules_by_user) if item[0] is not None
         )
 
         self.update_cache(sequence, members, ret_rules_by_user, state_group)
diff --git a/synapse/push/push_rule_evaluator.py b/synapse/push/push_rule_evaluator.py
index c3e6c5c258..cf735f7468 100644
--- a/synapse/push/push_rule_evaluator.py
+++ b/synapse/push/push_rule_evaluator.py
@@ -21,6 +21,8 @@ from synapse.types import UserID
 from synapse.util.caches import CACHE_SIZE_FACTOR, register_cache
 from synapse.util.caches.lrucache import LruCache
 
+from six import string_types
+
 logger = logging.getLogger(__name__)
 
 
@@ -238,7 +240,7 @@ def _flatten_dict(d, prefix=[], result=None):
     if result is None:
         result = {}
     for key, value in d.items():
-        if isinstance(value, basestring):
+        if isinstance(value, string_types):
             result[".".join(prefix + [key])] = value.lower()
         elif hasattr(value, "items"):
             _flatten_dict(value, prefix=(prefix + [key]), result=result)
diff --git a/synapse/replication/tcp/protocol.py b/synapse/replication/tcp/protocol.py
index 5995e5d553..a6280aae70 100644
--- a/synapse/replication/tcp/protocol.py
+++ b/synapse/replication/tcp/protocol.py
@@ -67,14 +67,14 @@ from prometheus_client import Counter
 
 from collections import defaultdict
 
+from six import iterkeys, iteritems
+
 import logging
 import struct
 import fcntl
 
 connection_close_counter = Counter(
-    "synapse_replication_tcp_protocol_close_reason", "", ["reason_type"],
-)
-
+    "synapse_replication_tcp_protocol_close_reason", "", ["reason_type"])
 
 # A list of all connected protocols. This allows us to send metrics about the
 # connections.
@@ -389,7 +389,7 @@ class ServerReplicationStreamProtocol(BaseReplicationStreamProtocol):
 
         if stream_name == "ALL":
             # Subscribe to all streams we're publishing to.
-            for stream in self.streamer.streams_by_name.iterkeys():
+            for stream in iterkeys(self.streamer.streams_by_name):
                 self.subscribe_to_stream(stream, token)
         else:
             self.subscribe_to_stream(stream_name, token)
@@ -495,7 +495,7 @@ class ClientReplicationStreamProtocol(BaseReplicationStreamProtocol):
         BaseReplicationStreamProtocol.connectionMade(self)
 
         # Once we've connected subscribe to the necessary streams
-        for stream_name, token in self.handler.get_streams_to_replicate().iteritems():
+        for stream_name, token in iteritems(self.handler.get_streams_to_replicate()):
             self.replicate(stream_name, token)
 
         # Tell the server if we have any users currently syncing (should only
@@ -622,7 +622,7 @@ tcp_inbound_commands = LaterGauge(
     lambda: {
         (k[0], p.name, p.conn_id): count
         for p in connected_connections
-        for k, count in p.inbound_commands_counter.items()
+        for k, count in iteritems(p.inbound_commands_counter.counts)
     })
 
 tcp_outbound_commands = LaterGauge(
@@ -630,7 +630,7 @@ tcp_outbound_commands = LaterGauge(
     lambda: {
         (k[0], p.name, p.conn_id): count
         for p in connected_connections
-        for k, count in p.outbound_commands_counter.items()
+        for k, count in iteritems(p.outbound_commands_counter.counts)
     })
 
 # number of updates received for each RDATA stream
diff --git a/synapse/replication/tcp/resource.py b/synapse/replication/tcp/resource.py
index 19987c06f0..63bd6d2652 100644
--- a/synapse/replication/tcp/resource.py
+++ b/synapse/replication/tcp/resource.py
@@ -27,6 +27,7 @@ from synapse.metrics import LaterGauge
 import logging
 
 from prometheus_client import Counter
+from six import itervalues
 
 stream_updates_counter = Counter("synapse_replication_tcp_resource_stream_updates",
                                  "", ["stream_name"])
@@ -81,7 +82,7 @@ class ReplicationStreamer(object):
         # We only support federation stream if federation sending hase been
         # disabled on the master.
         self.streams = [
-            stream(hs) for stream in STREAMS_MAP.itervalues()
+            stream(hs) for stream in itervalues(STREAMS_MAP)
             if stream != FederationStream or not hs.config.send_federation
         ]
 
diff --git a/synapse/rest/client/v1/presence.py b/synapse/rest/client/v1/presence.py
index 4a73813c58..647994bd53 100644
--- a/synapse/rest/client/v1/presence.py
+++ b/synapse/rest/client/v1/presence.py
@@ -23,6 +23,8 @@ from synapse.handlers.presence import format_user_presence_state
 from synapse.http.servlet import parse_json_object_from_request
 from .base import ClientV1RestServlet, client_path_patterns
 
+from six import string_types
+
 import logging
 
 logger = logging.getLogger(__name__)
@@ -71,7 +73,7 @@ class PresenceStatusRestServlet(ClientV1RestServlet):
 
             if "status_msg" in content:
                 state["status_msg"] = content.pop("status_msg")
-                if not isinstance(state["status_msg"], basestring):
+                if not isinstance(state["status_msg"], string_types):
                     raise SynapseError(400, "status_msg must be a string.")
 
             if content:
@@ -129,7 +131,7 @@ class PresenceListRestServlet(ClientV1RestServlet):
 
         if "invite" in content:
             for u in content["invite"]:
-                if not isinstance(u, basestring):
+                if not isinstance(u, string_types):
                     raise SynapseError(400, "Bad invite value.")
                 if len(u) == 0:
                     continue
@@ -140,7 +142,7 @@ class PresenceListRestServlet(ClientV1RestServlet):
 
         if "drop" in content:
             for u in content["drop"]:
-                if not isinstance(u, basestring):
+                if not isinstance(u, string_types):
                     raise SynapseError(400, "Bad drop value.")
                 if len(u) == 0:
                     continue
diff --git a/synapse/rest/media/v1/media_repository.py b/synapse/rest/media/v1/media_repository.py
index 9800ce7581..2ac767d2dc 100644
--- a/synapse/rest/media/v1/media_repository.py
+++ b/synapse/rest/media/v1/media_repository.py
@@ -48,6 +48,7 @@ import shutil
 import cgi
 import logging
 from six.moves.urllib import parse as urlparse
+from six import iteritems
 
 logger = logging.getLogger(__name__)
 
@@ -603,7 +604,7 @@ class MediaRepository(object):
                 thumbnails[(t_width, t_height, r_type)] = r_method
 
         # Now we generate the thumbnails for each dimension, store it
-        for (t_width, t_height, t_type), t_method in thumbnails.iteritems():
+        for (t_width, t_height, t_type), t_method in iteritems(thumbnails):
             # Generate the thumbnail
             if t_method == "crop":
                 t_byte_source = yield make_deferred_yieldable(threads.deferToThread(
diff --git a/synapse/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py
index 2839207abc..565cef2b8d 100644
--- a/synapse/rest/media/v1/preview_url_resource.py
+++ b/synapse/rest/media/v1/preview_url_resource.py
@@ -24,7 +24,9 @@ import shutil
 import sys
 import traceback
 import simplejson as json
-import urlparse
+
+from six.moves import urllib_parse as urlparse
+from six import string_types
 
 from twisted.web.server import NOT_DONE_YET
 from twisted.internet import defer
@@ -590,8 +592,8 @@ def _iterate_over_text(tree, *tags_to_ignore):
     # to be returned.
     elements = iter([tree])
     while True:
-        el = elements.next()
-        if isinstance(el, basestring):
+        el = next(elements)
+        if isinstance(el, string_types):
             yield el
         elif el is not None and el.tag not in tags_to_ignore:
             # el.text is the text before the first child, so we can immediately
diff --git a/synapse/server_notices/consent_server_notices.py b/synapse/server_notices/consent_server_notices.py
index 440f6b1cd4..bb74af1af5 100644
--- a/synapse/server_notices/consent_server_notices.py
+++ b/synapse/server_notices/consent_server_notices.py
@@ -14,10 +14,13 @@
 # limitations under the License.
 import logging
 
+from six import (iteritems, string_types)
 from twisted.internet import defer
 
 from synapse.api.errors import SynapseError
+from synapse.api.urls import ConsentURIBuilder
 from synapse.config import ConfigError
+from synapse.types import get_localpart_from_id
 
 logger = logging.getLogger(__name__)
 
@@ -39,6 +42,7 @@ class ConsentServerNotices(object):
 
         self._current_consent_version = hs.config.user_consent_version
         self._server_notice_content = hs.config.user_consent_server_notice_content
+        self._send_to_guests = hs.config.user_consent_server_notice_to_guests
 
         if self._server_notice_content is not None:
             if not self._server_notices_manager.is_enabled():
@@ -52,6 +56,8 @@ class ConsentServerNotices(object):
                     "key.",
                 )
 
+            self._consent_uri_builder = ConsentURIBuilder(hs.config)
+
     @defer.inlineCallbacks
     def maybe_send_server_notice_to_user(self, user_id):
         """Check if we need to send a notice to this user, and does so if so
@@ -73,6 +79,10 @@ class ConsentServerNotices(object):
         try:
             u = yield self._store.get_user_by_id(user_id)
 
+            if u["is_guest"] and not self._send_to_guests:
+                # don't send to guests
+                return
+
             if u["consent_version"] == self._current_consent_version:
                 # user has already consented
                 return
@@ -81,10 +91,18 @@ class ConsentServerNotices(object):
                 # we've already sent a notice to the user
                 return
 
-            # need to send a message
+            # need to send a message.
             try:
+                consent_uri = self._consent_uri_builder.build_user_consent_uri(
+                    get_localpart_from_id(user_id),
+                )
+                content = copy_with_str_subst(
+                    self._server_notice_content, {
+                        'consent_uri': consent_uri,
+                    },
+                )
                 yield self._server_notices_manager.send_notice(
-                    user_id, self._server_notice_content,
+                    user_id, content,
                 )
                 yield self._store.user_set_consent_server_notice_sent(
                     user_id, self._current_consent_version,
@@ -93,3 +111,27 @@ class ConsentServerNotices(object):
                 logger.error("Error sending server notice about user consent: %s", e)
         finally:
             self._users_in_progress.remove(user_id)
+
+
+def copy_with_str_subst(x, substitutions):
+    """Deep-copy a structure, carrying out string substitions on any strings
+
+    Args:
+        x (object): structure to be copied
+        substitutions (object): substitutions to be made - passed into the
+            string '%' operator
+
+    Returns:
+        copy of x
+    """
+    if isinstance(x, string_types):
+        return x % substitutions
+    if isinstance(x, dict):
+        return {
+            k: copy_with_str_subst(v, substitutions) for (k, v) in iteritems(x)
+        }
+    if isinstance(x, (list, tuple)):
+        return [copy_with_str_subst(y) for y in x]
+
+    # assume it's uninterested and can be shallow-copied.
+    return x
diff --git a/synapse/server_notices/server_notices_manager.py b/synapse/server_notices/server_notices_manager.py
index f535b9c9da..a26deace53 100644
--- a/synapse/server_notices/server_notices_manager.py
+++ b/synapse/server_notices/server_notices_manager.py
@@ -35,6 +35,7 @@ class ServerNoticesManager(object):
         self._config = hs.config
         self._room_creation_handler = hs.get_room_creation_handler()
         self._event_creation_handler = hs.get_event_creation_handler()
+        self._is_mine_id = hs.is_mine_id
 
     def is_enabled(self):
         """Checks if server notices are enabled on this server.
@@ -55,7 +56,7 @@ class ServerNoticesManager(object):
             event_content (dict): content of event to send
 
         Returns:
-            Deferrred[None]
+            Deferred[None]
         """
         room_id = yield self.get_notice_room_for_user(user_id)
 
@@ -89,6 +90,9 @@ class ServerNoticesManager(object):
         if not self.is_enabled():
             raise Exception("Server notices not enabled")
 
+        assert self._is_mine_id(user_id), \
+            "Cannot send server notices to remote users"
+
         rooms = yield self._store.get_rooms_for_user_where_membership_is(
             user_id, [Membership.INVITE, Membership.JOIN],
         )
@@ -109,6 +113,19 @@ class ServerNoticesManager(object):
         # apparently no existing notice room: create a new one
         logger.info("Creating server notices room for %s", user_id)
 
+        # see if we want to override the profile info for the server user.
+        # note that if we want to override either the display name or the
+        # avatar, we have to use both.
+        join_profile = None
+        if (
+            self._config.server_notices_mxid_display_name is not None or
+            self._config.server_notices_mxid_avatar_url is not None
+        ):
+            join_profile = {
+                "displayname": self._config.server_notices_mxid_display_name,
+                "avatar_url": self._config.server_notices_mxid_avatar_url,
+            }
+
         requester = create_requester(system_mxid)
         info = yield self._room_creation_handler.create_room(
             requester,
@@ -121,9 +138,7 @@ class ServerNoticesManager(object):
                 "invite": (user_id,)
             },
             ratelimit=False,
-            creator_join_profile={
-                "displayname": self._config.server_notices_mxid_display_name,
-            },
+            creator_join_profile=join_profile,
         )
         room_id = info['room_id']
 
diff --git a/synapse/server_notices/worker_server_notices_sender.py b/synapse/server_notices/worker_server_notices_sender.py
index 25abb4ccf5..4a133026c3 100644
--- a/synapse/server_notices/worker_server_notices_sender.py
+++ b/synapse/server_notices/worker_server_notices_sender.py
@@ -32,7 +32,7 @@ class WorkerServerNoticesSender(object):
         Returns:
             Deferred
         """
-        return defer.succeed()
+        return defer.succeed(None)
 
     def on_user_ip(self, user_id):
         """Called on the master when a worker process saw a client request.
diff --git a/synapse/state.py b/synapse/state.py
index 26093c8434..b8c27c6815 100644
--- a/synapse/state.py
+++ b/synapse/state.py
@@ -32,6 +32,8 @@ from frozendict import frozendict
 import logging
 import hashlib
 
+from six import iteritems, itervalues
+
 logger = logging.getLogger(__name__)
 
 
@@ -132,7 +134,7 @@ class StateHandler(object):
 
         state_map = yield self.store.get_events(state.values(), get_prev_content=False)
         state = {
-            key: state_map[e_id] for key, e_id in state.iteritems() if e_id in state_map
+            key: state_map[e_id] for key, e_id in iteritems(state) if e_id in state_map
         }
 
         defer.returnValue(state)
@@ -338,7 +340,7 @@ class StateHandler(object):
         )
 
         if len(state_groups_ids) == 1:
-            name, state_list = state_groups_ids.items().pop()
+            name, state_list = list(state_groups_ids.items()).pop()
 
             prev_group, delta_ids = yield self.store.get_state_group_delta(name)
 
@@ -378,7 +380,7 @@ class StateHandler(object):
             new_state = resolve_events_with_state_map(state_set_ids, state_map)
 
         new_state = {
-            key: state_map[ev_id] for key, ev_id in new_state.iteritems()
+            key: state_map[ev_id] for key, ev_id in iteritems(new_state)
         }
 
         return new_state
@@ -458,15 +460,15 @@ class StateResolutionHandler(object):
             # build a map from state key to the event_ids which set that state.
             # dict[(str, str), set[str])
             state = {}
-            for st in state_groups_ids.itervalues():
-                for key, e_id in st.iteritems():
+            for st in itervalues(state_groups_ids):
+                for key, e_id in iteritems(st):
                     state.setdefault(key, set()).add(e_id)
 
             # build a map from state key to the event_ids which set that state,
             # including only those where there are state keys in conflict.
             conflicted_state = {
                 k: list(v)
-                for k, v in state.iteritems()
+                for k, v in iteritems(state)
                 if len(v) > 1
             }
 
@@ -474,13 +476,13 @@ class StateResolutionHandler(object):
                 logger.info("Resolving conflicted state for %r", room_id)
                 with Measure(self.clock, "state._resolve_events"):
                     new_state = yield resolve_events_with_factory(
-                        state_groups_ids.values(),
+                        list(state_groups_ids.values()),
                         event_map=event_map,
                         state_map_factory=state_map_factory,
                     )
             else:
                 new_state = {
-                    key: e_ids.pop() for key, e_ids in state.iteritems()
+                    key: e_ids.pop() for key, e_ids in iteritems(state)
                 }
 
             with Measure(self.clock, "state.create_group_ids"):
@@ -489,8 +491,8 @@ class StateResolutionHandler(object):
                 # which will be used as a cache key for future resolutions, but
                 # not get persisted.
                 state_group = None
-                new_state_event_ids = frozenset(new_state.itervalues())
-                for sg, events in state_groups_ids.iteritems():
+                new_state_event_ids = frozenset(itervalues(new_state))
+                for sg, events in iteritems(state_groups_ids):
                     if new_state_event_ids == frozenset(e_id for e_id in events):
                         state_group = sg
                         break
@@ -501,11 +503,11 @@ class StateResolutionHandler(object):
 
                 prev_group = None
                 delta_ids = None
-                for old_group, old_ids in state_groups_ids.iteritems():
+                for old_group, old_ids in iteritems(state_groups_ids):
                     if not set(new_state) - set(old_ids):
                         n_delta_ids = {
                             k: v
-                            for k, v in new_state.iteritems()
+                            for k, v in iteritems(new_state)
                             if old_ids.get(k) != v
                         }
                         if not delta_ids or len(n_delta_ids) < len(delta_ids):
@@ -527,7 +529,7 @@ class StateResolutionHandler(object):
 
 def _ordered_events(events):
     def key_func(e):
-        return -int(e.depth), hashlib.sha1(e.event_id).hexdigest()
+        return -int(e.depth), hashlib.sha1(e.event_id.encode()).hexdigest()
 
     return sorted(events, key=key_func)
 
@@ -584,7 +586,7 @@ def _seperate(state_sets):
     conflicted_state = {}
 
     for state_set in state_sets[1:]:
-        for key, value in state_set.iteritems():
+        for key, value in iteritems(state_set):
             # Check if there is an unconflicted entry for the state key.
             unconflicted_value = unconflicted_state.get(key)
             if unconflicted_value is None:
@@ -640,7 +642,7 @@ def resolve_events_with_factory(state_sets, event_map, state_map_factory):
 
     needed_events = set(
         event_id
-        for event_ids in conflicted_state.itervalues()
+        for event_ids in itervalues(conflicted_state)
         for event_id in event_ids
     )
     if event_map is not None:
@@ -662,7 +664,7 @@ def resolve_events_with_factory(state_sets, event_map, state_map_factory):
         unconflicted_state, conflicted_state, state_map
     )
 
-    new_needed_events = set(auth_events.itervalues())
+    new_needed_events = set(itervalues(auth_events))
     new_needed_events -= needed_events
     if event_map is not None:
         new_needed_events -= set(event_map.iterkeys())
@@ -679,7 +681,7 @@ def resolve_events_with_factory(state_sets, event_map, state_map_factory):
 
 def _create_auth_events_from_maps(unconflicted_state, conflicted_state, state_map):
     auth_events = {}
-    for event_ids in conflicted_state.itervalues():
+    for event_ids in itervalues(conflicted_state):
         for event_id in event_ids:
             if event_id in state_map:
                 keys = event_auth.auth_types_for_event(state_map[event_id])
@@ -694,7 +696,7 @@ def _create_auth_events_from_maps(unconflicted_state, conflicted_state, state_ma
 def _resolve_with_state(unconflicted_state_ids, conflicted_state_ds, auth_event_ids,
                         state_map):
     conflicted_state = {}
-    for key, event_ids in conflicted_state_ds.iteritems():
+    for key, event_ids in iteritems(conflicted_state_ds):
         events = [state_map[ev_id] for ev_id in event_ids if ev_id in state_map]
         if len(events) > 1:
             conflicted_state[key] = events
@@ -703,7 +705,7 @@ def _resolve_with_state(unconflicted_state_ids, conflicted_state_ds, auth_event_
 
     auth_events = {
         key: state_map[ev_id]
-        for key, ev_id in auth_event_ids.iteritems()
+        for key, ev_id in iteritems(auth_event_ids)
         if ev_id in state_map
     }
 
@@ -716,7 +718,7 @@ def _resolve_with_state(unconflicted_state_ids, conflicted_state_ds, auth_event_
         raise
 
     new_state = unconflicted_state_ids
-    for key, event in resolved_state.iteritems():
+    for key, event in iteritems(resolved_state):
         new_state[key] = event.event_id
 
     return new_state
@@ -741,7 +743,7 @@ def _resolve_state_events(conflicted_state, auth_events):
 
     auth_events.update(resolved_state)
 
-    for key, events in conflicted_state.iteritems():
+    for key, events in iteritems(conflicted_state):
         if key[0] == EventTypes.JoinRules:
             logger.debug("Resolving conflicted join rules %r", events)
             resolved_state[key] = _resolve_auth_events(
@@ -751,7 +753,7 @@ def _resolve_state_events(conflicted_state, auth_events):
 
     auth_events.update(resolved_state)
 
-    for key, events in conflicted_state.iteritems():
+    for key, events in iteritems(conflicted_state):
         if key[0] == EventTypes.Member:
             logger.debug("Resolving conflicted member lists %r", events)
             resolved_state[key] = _resolve_auth_events(
@@ -761,7 +763,7 @@ def _resolve_state_events(conflicted_state, auth_events):
 
     auth_events.update(resolved_state)
 
-    for key, events in conflicted_state.iteritems():
+    for key, events in iteritems(conflicted_state):
         if key not in resolved_state:
             logger.debug("Resolving conflicted state %r:%r", key, events)
             resolved_state[key] = _resolve_normal_events(
diff --git a/synapse/storage/_base.py b/synapse/storage/_base.py
index d1b625dc30..d963af5c89 100644
--- a/synapse/storage/_base.py
+++ b/synapse/storage/_base.py
@@ -27,9 +27,17 @@ import sys
 import time
 import threading
 
+from six import itervalues, iterkeys, iteritems
+from six.moves import intern, range
 
 logger = logging.getLogger(__name__)
 
+try:
+    MAX_TXN_ID = sys.maxint - 1
+except AttributeError:
+    # python 3 does not have a maximum int value
+    MAX_TXN_ID = 2**63 - 1
+
 sql_logger = logging.getLogger("synapse.storage.SQL")
 transaction_logger = logging.getLogger("synapse.storage.txn")
 perf_logger = logging.getLogger("synapse.storage.TIME")
@@ -134,7 +142,7 @@ class PerformanceCounters(object):
 
     def interval(self, interval_duration, limit=3):
         counters = []
-        for name, (count, cum_time) in self.current_counters.iteritems():
+        for name, (count, cum_time) in iteritems(self.current_counters):
             prev_count, prev_time = self.previous_counters.get(name, (0, 0))
             counters.append((
                 (cum_time - prev_time) / interval_duration,
@@ -219,7 +227,7 @@ class SQLBaseStore(object):
 
         # We don't really need these to be unique, so lets stop it from
         # growing really large.
-        self._TXN_ID = (self._TXN_ID + 1) % (sys.maxint - 1)
+        self._TXN_ID = (self._TXN_ID + 1) % (MAX_TXN_ID)
 
         name = "%s-%x" % (desc, txn_id, )
 
@@ -540,7 +548,7 @@ class SQLBaseStore(object):
             ", ".join("%s = ?" % (k,) for k in values),
             " AND ".join("%s = ?" % (k,) for k in keyvalues)
         )
-        sqlargs = values.values() + keyvalues.values()
+        sqlargs = list(values.values()) + list(keyvalues.values())
 
         txn.execute(sql, sqlargs)
         if txn.rowcount > 0:
@@ -558,7 +566,7 @@ class SQLBaseStore(object):
             ", ".join(k for k in allvalues),
             ", ".join("?" for _ in allvalues)
         )
-        txn.execute(sql, allvalues.values())
+        txn.execute(sql, list(allvalues.values()))
         # successfully inserted
         return True
 
@@ -626,8 +634,8 @@ class SQLBaseStore(object):
         }
 
         if keyvalues:
-            sql += " WHERE %s" % " AND ".join("%s = ?" % k for k in keyvalues.iterkeys())
-            txn.execute(sql, keyvalues.values())
+            sql += " WHERE %s" % " AND ".join("%s = ?" % k for k in iterkeys(keyvalues))
+            txn.execute(sql, list(keyvalues.values()))
         else:
             txn.execute(sql)
 
@@ -691,7 +699,7 @@ class SQLBaseStore(object):
                 table,
                 " AND ".join("%s = ?" % (k, ) for k in keyvalues)
             )
-            txn.execute(sql, keyvalues.values())
+            txn.execute(sql, list(keyvalues.values()))
         else:
             sql = "SELECT %s FROM %s" % (
                 ", ".join(retcols),
@@ -722,9 +730,12 @@ class SQLBaseStore(object):
         if not iterable:
             defer.returnValue(results)
 
+        # iterables can not be sliced, so convert it to a list first
+        it_list = list(iterable)
+
         chunks = [
-            iterable[i:i + batch_size]
-            for i in xrange(0, len(iterable), batch_size)
+            it_list[i:i + batch_size]
+            for i in range(0, len(it_list), batch_size)
         ]
         for chunk in chunks:
             rows = yield self.runInteraction(
@@ -764,7 +775,7 @@ class SQLBaseStore(object):
         )
         values.extend(iterable)
 
-        for key, value in keyvalues.iteritems():
+        for key, value in iteritems(keyvalues):
             clauses.append("%s = ?" % (key,))
             values.append(value)
 
@@ -787,7 +798,7 @@ class SQLBaseStore(object):
     @staticmethod
     def _simple_update_txn(txn, table, keyvalues, updatevalues):
         if keyvalues:
-            where = "WHERE %s" % " AND ".join("%s = ?" % k for k in keyvalues.iterkeys())
+            where = "WHERE %s" % " AND ".join("%s = ?" % k for k in iterkeys(keyvalues))
         else:
             where = ""
 
@@ -799,7 +810,7 @@ class SQLBaseStore(object):
 
         txn.execute(
             update_sql,
-            updatevalues.values() + keyvalues.values()
+            list(updatevalues.values()) + list(keyvalues.values())
         )
 
         return txn.rowcount
@@ -847,7 +858,7 @@ class SQLBaseStore(object):
             " AND ".join("%s = ?" % (k,) for k in keyvalues)
         )
 
-        txn.execute(select_sql, keyvalues.values())
+        txn.execute(select_sql, list(keyvalues.values()))
 
         row = txn.fetchone()
         if not row:
@@ -885,7 +896,7 @@ class SQLBaseStore(object):
             " AND ".join("%s = ?" % (k, ) for k in keyvalues)
         )
 
-        txn.execute(sql, keyvalues.values())
+        txn.execute(sql, list(keyvalues.values()))
         if txn.rowcount == 0:
             raise StoreError(404, "No row found")
         if txn.rowcount > 1:
@@ -903,7 +914,7 @@ class SQLBaseStore(object):
             " AND ".join("%s = ?" % (k, ) for k in keyvalues)
         )
 
-        return txn.execute(sql, keyvalues.values())
+        return txn.execute(sql, list(keyvalues.values()))
 
     def _simple_delete_many(self, table, column, iterable, keyvalues, desc):
         return self.runInteraction(
@@ -935,7 +946,7 @@ class SQLBaseStore(object):
         )
         values.extend(iterable)
 
-        for key, value in keyvalues.iteritems():
+        for key, value in iteritems(keyvalues):
             clauses.append("%s = ?" % (key,))
             values.append(value)
 
@@ -975,7 +986,7 @@ class SQLBaseStore(object):
         txn.close()
 
         if cache:
-            min_val = min(cache.itervalues())
+            min_val = min(itervalues(cache))
         else:
             min_val = max_value
 
@@ -1090,7 +1101,7 @@ class SQLBaseStore(object):
                 " AND ".join("%s = ?" % (k,) for k in keyvalues),
                 " ? ASC LIMIT ? OFFSET ?"
             )
-            txn.execute(sql, keyvalues.values() + pagevalues)
+            txn.execute(sql, list(keyvalues.values()) + list(pagevalues))
         else:
             sql = "SELECT %s FROM %s ORDER BY %s" % (
                 ", ".join(retcols),
diff --git a/synapse/storage/client_ips.py b/synapse/storage/client_ips.py
index ba46907737..ce338514e8 100644
--- a/synapse/storage/client_ips.py
+++ b/synapse/storage/client_ips.py
@@ -22,6 +22,8 @@ from . import background_updates
 
 from synapse.util.caches import CACHE_SIZE_FACTOR
 
+from six import iteritems
+
 
 logger = logging.getLogger(__name__)
 
@@ -99,7 +101,7 @@ class ClientIpStore(background_updates.BackgroundUpdateStore):
     def _update_client_ips_batch_txn(self, txn, to_update):
         self.database_engine.lock_table(txn, "user_ips")
 
-        for entry in to_update.iteritems():
+        for entry in iteritems(to_update):
             (user_id, access_token, ip), (user_agent, device_id, last_seen) = entry
 
             self._simple_upsert_txn(
@@ -231,5 +233,5 @@ class ClientIpStore(background_updates.BackgroundUpdateStore):
                 "user_agent": user_agent,
                 "last_seen": last_seen,
             }
-            for (access_token, ip), (user_agent, last_seen) in results.iteritems()
+            for (access_token, ip), (user_agent, last_seen) in iteritems(results)
         ))
diff --git a/synapse/storage/devices.py b/synapse/storage/devices.py
index 712106b83a..d149d8392e 100644
--- a/synapse/storage/devices.py
+++ b/synapse/storage/devices.py
@@ -21,6 +21,7 @@ from synapse.api.errors import StoreError
 from ._base import SQLBaseStore, Cache
 from synapse.util.caches.descriptors import cached, cachedList, cachedInlineCallbacks
 
+from six import itervalues, iteritems
 
 logger = logging.getLogger(__name__)
 
@@ -360,7 +361,7 @@ class DeviceStore(SQLBaseStore):
             return (now_stream_id, [])
 
         if len(query_map) >= 20:
-            now_stream_id = max(stream_id for stream_id in query_map.itervalues())
+            now_stream_id = max(stream_id for stream_id in itervalues(query_map))
 
         devices = self._get_e2e_device_keys_txn(
             txn, query_map.keys(), include_all_devices=True
@@ -373,13 +374,13 @@ class DeviceStore(SQLBaseStore):
         """
 
         results = []
-        for user_id, user_devices in devices.iteritems():
+        for user_id, user_devices in iteritems(devices):
             # The prev_id for the first row is always the last row before
             # `from_stream_id`
             txn.execute(prev_sent_id_sql, (destination, user_id, from_stream_id))
             rows = txn.fetchall()
             prev_id = rows[0][0]
-            for device_id, device in user_devices.iteritems():
+            for device_id, device in iteritems(user_devices):
                 stream_id = query_map[(user_id, device_id)]
                 result = {
                     "user_id": user_id,
@@ -483,7 +484,7 @@ class DeviceStore(SQLBaseStore):
         if devices:
             user_devices = devices[user_id]
             results = []
-            for device_id, device in user_devices.iteritems():
+            for device_id, device in iteritems(user_devices):
                 result = {
                     "device_id": device_id,
                 }
diff --git a/synapse/storage/end_to_end_keys.py b/synapse/storage/end_to_end_keys.py
index ff8538ddf8..b146487943 100644
--- a/synapse/storage/end_to_end_keys.py
+++ b/synapse/storage/end_to_end_keys.py
@@ -21,6 +21,8 @@ import simplejson as json
 
 from ._base import SQLBaseStore
 
+from six import iteritems
+
 
 class EndToEndKeyStore(SQLBaseStore):
     def set_e2e_device_keys(self, user_id, device_id, time_now, device_keys):
@@ -81,8 +83,8 @@ class EndToEndKeyStore(SQLBaseStore):
             query_list, include_all_devices,
         )
 
-        for user_id, device_keys in results.iteritems():
-            for device_id, device_info in device_keys.iteritems():
+        for user_id, device_keys in iteritems(results):
+            for device_id, device_info in iteritems(device_keys):
                 device_info["keys"] = json.loads(device_info.pop("key_json"))
 
         defer.returnValue(results)
diff --git a/synapse/storage/event_push_actions.py b/synapse/storage/event_push_actions.py
index f084a5f54b..d0350ee5fe 100644
--- a/synapse/storage/event_push_actions.py
+++ b/synapse/storage/event_push_actions.py
@@ -22,6 +22,8 @@ from synapse.util.caches.descriptors import cachedInlineCallbacks
 import logging
 import simplejson as json
 
+from six import iteritems
+
 logger = logging.getLogger(__name__)
 
 
@@ -420,7 +422,7 @@ class EventPushActionsWorkerStore(SQLBaseStore):
 
             txn.executemany(sql, (
                 _gen_entry(user_id, actions)
-                for user_id, actions in user_id_actions.iteritems()
+                for user_id, actions in iteritems(user_id_actions)
             ))
 
         return self.runInteraction(
diff --git a/synapse/storage/events_worker.py b/synapse/storage/events_worker.py
index ba834854e1..32d9d00ffb 100644
--- a/synapse/storage/events_worker.py
+++ b/synapse/storage/events_worker.py
@@ -337,7 +337,7 @@ class EventsWorkerStore(SQLBaseStore):
     def _fetch_event_rows(self, txn, events):
         rows = []
         N = 200
-        for i in range(1 + len(events) / N):
+        for i in range(1 + len(events) // N):
             evs = events[i * N:(i + 1) * N]
             if not evs:
                 break
diff --git a/synapse/storage/filtering.py b/synapse/storage/filtering.py
index 78b1e30945..2e2763126d 100644
--- a/synapse/storage/filtering.py
+++ b/synapse/storage/filtering.py
@@ -44,7 +44,7 @@ class FilteringStore(SQLBaseStore):
             desc="get_user_filter",
         )
 
-        defer.returnValue(json.loads(str(def_json).decode("utf-8")))
+        defer.returnValue(json.loads(bytes(def_json).decode("utf-8")))
 
     def add_user_filter(self, user_localpart, user_filter):
         def_json = encode_canonical_json(user_filter)
diff --git a/synapse/storage/keys.py b/synapse/storage/keys.py
index 87aeaf71d6..0540c2b0b1 100644
--- a/synapse/storage/keys.py
+++ b/synapse/storage/keys.py
@@ -92,7 +92,7 @@ class KeyStore(SQLBaseStore):
 
         if verify_key_bytes:
             defer.returnValue(decode_verify_key_bytes(
-                key_id, str(verify_key_bytes)
+                key_id, bytes(verify_key_bytes)
             ))
 
     @defer.inlineCallbacks
diff --git a/synapse/storage/roommember.py b/synapse/storage/roommember.py
index 6a861943a2..7bfc3d91b5 100644
--- a/synapse/storage/roommember.py
+++ b/synapse/storage/roommember.py
@@ -30,6 +30,8 @@ from synapse.types import get_domain_from_id
 import logging
 import simplejson as json
 
+from six import itervalues, iteritems
+
 logger = logging.getLogger(__name__)
 
 
@@ -272,7 +274,7 @@ class RoomMemberWorkerStore(EventsWorkerStore):
         users_in_room = {}
         member_event_ids = [
             e_id
-            for key, e_id in current_state_ids.iteritems()
+            for key, e_id in iteritems(current_state_ids)
             if key[0] == EventTypes.Member
         ]
 
@@ -289,7 +291,7 @@ class RoomMemberWorkerStore(EventsWorkerStore):
                     users_in_room = dict(prev_res)
                     member_event_ids = [
                         e_id
-                        for key, e_id in context.delta_ids.iteritems()
+                        for key, e_id in iteritems(context.delta_ids)
                         if key[0] == EventTypes.Member
                     ]
                     for etype, state_key in context.delta_ids:
@@ -741,7 +743,7 @@ class _JoinedHostsCache(object):
             if state_entry.state_group == self.state_group:
                 pass
             elif state_entry.prev_group == self.state_group:
-                for (typ, state_key), event_id in state_entry.delta_ids.iteritems():
+                for (typ, state_key), event_id in iteritems(state_entry.delta_ids):
                     if typ != EventTypes.Member:
                         continue
 
@@ -771,7 +773,7 @@ class _JoinedHostsCache(object):
                 self.state_group = state_entry.state_group
             else:
                 self.state_group = object()
-            self._len = sum(len(v) for v in self.hosts_to_joined_users.itervalues())
+            self._len = sum(len(v) for v in itervalues(self.hosts_to_joined_users))
         defer.returnValue(frozenset(self.hosts_to_joined_users))
 
     def __len__(self):
diff --git a/synapse/storage/stream.py b/synapse/storage/stream.py
index ea24710ad8..fb463c525a 100644
--- a/synapse/storage/stream.py
+++ b/synapse/storage/stream.py
@@ -684,8 +684,7 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
                 results to only those before
             direction(char): Either 'b' or 'f' to indicate whether we are
                 paginating forwards or backwards from `from_key`.
-            limit (int): The maximum number of events to return. Zero or less
-                means no limit.
+            limit (int): The maximum number of events to return.
             event_filter (Filter|None): If provided filters the events to
                 those that match the filter.
 
@@ -694,6 +693,9 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
             as a list of _EventDictReturn and a token that points to the end
             of the result set.
         """
+
+        assert int(limit) >= 0
+
         # Tokens really represent positions between elements, but we use
         # the convention of pointing to the event before the gap. Hence
         # we have a bit of asymmetry when it comes to equalities.
@@ -723,22 +725,17 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
             bounds += " AND " + filter_clause
             args.extend(filter_args)
 
-        if int(limit) > 0:
-            args.append(int(limit))
-            limit_str = " LIMIT ?"
-        else:
-            limit_str = ""
+        args.append(int(limit))
 
         sql = (
             "SELECT event_id, topological_ordering, stream_ordering"
             " FROM events"
             " WHERE outlier = ? AND room_id = ? AND %(bounds)s"
             " ORDER BY topological_ordering %(order)s,"
-            " stream_ordering %(order)s %(limit)s"
+            " stream_ordering %(order)s LIMIT ?"
         ) % {
             "bounds": bounds,
             "order": order,
-            "limit": limit_str
         }
 
         txn.execute(sql, args)
diff --git a/synapse/util/__init__.py b/synapse/util/__init__.py
index 814a7bf71b..fc11e26623 100644
--- a/synapse/util/__init__.py
+++ b/synapse/util/__init__.py
@@ -20,6 +20,8 @@ from twisted.internet import defer, reactor, task
 import time
 import logging
 
+from itertools import islice
+
 logger = logging.getLogger(__name__)
 
 
@@ -79,3 +81,19 @@ class Clock(object):
         except Exception:
             if not ignore_errs:
                 raise
+
+
+def batch_iter(iterable, size):
+    """batch an iterable up into tuples with a maximum size
+
+    Args:
+        iterable (iterable): the iterable to slice
+        size (int): the maximum batch size
+
+    Returns:
+        an iterator over the chunks
+    """
+    # make sure we can deal with iterables like lists too
+    sourceiter = iter(iterable)
+    # call islice until it returns an empty tuple
+    return iter(lambda: tuple(islice(sourceiter, size)), ())
diff --git a/synapse/util/caches/__init__.py b/synapse/util/caches/__init__.py
index e0c22df249..d968b71e7a 100644
--- a/synapse/util/caches/__init__.py
+++ b/synapse/util/caches/__init__.py
@@ -17,6 +17,9 @@ from prometheus_client.core import Gauge, REGISTRY, GaugeMetricFamily
 
 import os
 
+from six.moves import intern
+import six
+
 CACHE_SIZE_FACTOR = float(os.environ.get("SYNAPSE_CACHE_FACTOR", 0.5))
 
 caches_by_name = {}
@@ -110,7 +113,9 @@ def intern_string(string):
         return None
 
     try:
-        string = string.encode("ascii")
+        if six.PY2:
+            string = string.encode("ascii")
+
         return intern(string)
     except UnicodeEncodeError:
         return string