Update black, and run auto formatting over the codebase (#9381)

 - Update black version to the latest
 - Run black auto formatting over the codebase
    - Run autoformatting according to [`docs/code_style.md
`](https://github.com/matrix-org/synapse/blob/80d6dc9783aa80886a133756028984dbf8920168/docs/code_style.md)
 - Update `code_style.md` docs around installing black to use the correct version

4 files changed, 7 insertions, 5 deletions

diff --git a/synapse/events/builder.py b/synapse/events/builder.py
index 07df258e6e..c1c0426f6e 100644
--- a/synapse/events/builder.py
+++ b/synapse/events/builder.py
@@ -98,7 +98,9 @@ class EventBuilder:
         return self._state_key is not None
 
     async def build(
-        self, prev_event_ids: List[str], auth_event_ids: Optional[List[str]],
+        self,
+        prev_event_ids: List[str],
+        auth_event_ids: Optional[List[str]],
     ) -> EventBase:
         """Transform into a fully signed and hashed event
 
diff --git a/synapse/events/snapshot.py b/synapse/events/snapshot.py
index afecafe15c..7295df74fe 100644
--- a/synapse/events/snapshot.py
+++ b/synapse/events/snapshot.py
@@ -341,8 +341,7 @@ def _encode_state_dict(state_dict):
 
 
 def _decode_state_dict(input):
-    """Decodes a state dict encoded using `_encode_state_dict` above
-    """
+    """Decodes a state dict encoded using `_encode_state_dict` above"""
     if input is None:
         return None
 
diff --git a/synapse/events/third_party_rules.py b/synapse/events/third_party_rules.py
index 77fbd3f68a..02bce8b5c9 100644
--- a/synapse/events/third_party_rules.py
+++ b/synapse/events/third_party_rules.py
@@ -40,7 +40,8 @@ class ThirdPartyEventRules:
 
         if module is not None:
             self.third_party_rules = module(
-                config=config, module_api=hs.get_module_api(),
+                config=config,
+                module_api=hs.get_module_api(),
             )
 
     async def check_event_allowed(
diff --git a/synapse/events/utils.py b/synapse/events/utils.py
index 9c22e33813..7ca5c9940a 100644
--- a/synapse/events/utils.py
+++ b/synapse/events/utils.py
@@ -34,7 +34,7 @@ SPLIT_FIELD_REGEX = re.compile(r"(?<!\\)\.")
 
 
 def prune_event(event: EventBase) -> EventBase:
-    """ Returns a pruned version of the given event, which removes all keys we
+    """Returns a pruned version of the given event, which removes all keys we
     don't know about or think could potentially be dodgy.
 
     This is used when we "redact" an event. We want to remove all fields that