6 files changed, 24 insertions, 23 deletions
diff --git a/synapse/util/async_helpers.py b/synapse/util/async_helpers.py
index 804dbca443..5c4de2e69f 100644
--- a/synapse/util/async_helpers.py
+++ b/synapse/util/async_helpers.py
@@ -86,11 +86,12 @@ class ObservableDeferred(object):
 
         deferred.addCallbacks(callback, errback)
 
-    def observe(self):
+    def observe(self) -> defer.Deferred:
         """Observe the underlying deferred.
 
-        Can return either a deferred if the underlying deferred is still pending
-        (or has failed), or the actual value. Callers may need to use maybeDeferred.
+        This returns a brand new deferred that is resolved when the underlying
+        deferred is resolved. Interacting with the returned deferred does not
+        effect the underdlying deferred.
         """
         if not self._result:
             d = defer.Deferred()
@@ -105,7 +106,7 @@ class ObservableDeferred(object):
             return d
         else:
             success, res = self._result
-            return res if success else defer.fail(res)
+            return defer.succeed(res) if success else defer.fail(res)
 
     def observers(self):
         return self._observers
@@ -138,7 +139,7 @@ def concurrently_execute(func, args, limit):
     the number of concurrent executions.
 
     Args:
-        func (func): Function to execute, should return a deferred.
+        func (func): Function to execute, should return a deferred or coroutine.
         args (list): List of arguments to pass to func, each invocation of func
             gets a signle argument.
         limit (int): Maximum number of conccurent executions.
@@ -148,11 +149,10 @@ def concurrently_execute(func, args, limit):
     """
     it = iter(args)
 
-    @defer.inlineCallbacks
-    def _concurrently_execute_inner():
+    async def _concurrently_execute_inner():
         try:
             while True:
-                yield func(next(it))
+                await maybe_awaitable(func(next(it)))
         except StopIteration:
             pass
 
@@ -309,7 +309,7 @@ class Linearizer(object):
                 )
 
             else:
-                logger.warn(
+                logger.warning(
                     "Unexpected exception waiting for linearizer lock %r for key %r",
                     self.name,
                     key,
diff --git a/synapse/util/caches/__init__.py b/synapse/util/caches/__init__.py
index 43fd65d693..da5077b471 100644
--- a/synapse/util/caches/__init__.py
+++ b/synapse/util/caches/__init__.py
@@ -107,7 +107,7 @@ def register_cache(cache_type, cache_name, cache, collect_callback=None):
                 if collect_callback:
                     collect_callback()
             except Exception as e:
-                logger.warn("Error calculating metrics for %s: %s", cache_name, e)
+                logger.warning("Error calculating metrics for %s: %s", cache_name, e)
                 raise
 
             yield GaugeMetricFamily("__unused", "")
diff --git a/synapse/util/caches/descriptors.py b/synapse/util/caches/descriptors.py
index 5ac2530a6a..0e8da27f53 100644
--- a/synapse/util/caches/descriptors.py
+++ b/synapse/util/caches/descriptors.py
@@ -438,7 +438,7 @@ class CacheDescriptor(_CacheDescriptorBase):
                 if isinstance(cached_result_d, ObservableDeferred):
                     observer = cached_result_d.observe()
                 else:
-                    observer = cached_result_d
+                    observer = defer.succeed(cached_result_d)
 
             except KeyError:
                 ret = defer.maybeDeferred(
@@ -482,9 +482,8 @@ class CacheListDescriptor(_CacheDescriptorBase):
     Given a list of keys it looks in the cache to find any hits, then passes
     the list of missing keys to the wrapped function.
 
-    Once wrapped, the function returns either a Deferred which resolves to
-    the list of results, or (if all results were cached), just the list of
-    results.
+    Once wrapped, the function returns a Deferred which resolves to the list
+    of results.
     """
 
     def __init__(
@@ -618,7 +617,7 @@ class CacheListDescriptor(_CacheDescriptorBase):
                 )
                 return make_deferred_yieldable(d)
             else:
-                return results
+                return defer.succeed(results)
 
         obj.__dict__[self.orig.__name__] = wrapped
 
diff --git a/synapse/util/metrics.py b/synapse/util/metrics.py
index 4b1bcdf23c..3286804322 100644
--- a/synapse/util/metrics.py
+++ b/synapse/util/metrics.py
@@ -119,7 +119,7 @@ class Measure(object):
         context = LoggingContext.current_context()
 
         if context != self.start_context:
-            logger.warn(
+            logger.warning(
                 "Context has unexpectedly changed from '%s' to '%s'. (%r)",
                 self.start_context,
                 context,
@@ -128,7 +128,7 @@ class Measure(object):
             return
 
         if not context:
-            logger.warn("Expected context. (%r)", self.name)
+            logger.warning("Expected context. (%r)", self.name)
             return
 
         current = context.get_resource_usage()
@@ -140,7 +140,7 @@ class Measure(object):
             block_db_txn_duration.labels(self.name).inc(usage.db_txn_duration_sec)
             block_db_sched_duration.labels(self.name).inc(usage.db_sched_duration_sec)
         except ValueError:
-            logger.warn(
+            logger.warning(
                 "Failed to save metrics! OLD: %r, NEW: %r", self.start_usage, current
             )
 
diff --git a/synapse/util/rlimit.py b/synapse/util/rlimit.py
index 6c0f2bb0cf..207cd17c2a 100644
--- a/synapse/util/rlimit.py
+++ b/synapse/util/rlimit.py
@@ -33,4 +33,4 @@ def change_resource_limit(soft_file_no):
             resource.RLIMIT_CORE, (resource.RLIM_INFINITY, resource.RLIM_INFINITY)
         )
     except (ValueError, resource.error) as e:
-        logger.warn("Failed to set file or core limit: %s", e)
+        logger.warning("Failed to set file or core limit: %s", e)
diff --git a/synapse/util/versionstring.py b/synapse/util/versionstring.py
index fa404b9d75..ab7d03af3a 100644
--- a/synapse/util/versionstring.py
+++ b/synapse/util/versionstring.py
@@ -42,6 +42,7 @@ def get_version_string(module):
     try:
         null = open(os.devnull, "w")
         cwd = os.path.dirname(os.path.abspath(module.__file__))
+
         try:
             git_branch = (
                 subprocess.check_output(
@@ -51,7 +52,8 @@ def get_version_string(module):
                 .decode("ascii")
             )
             git_branch = "b=" + git_branch
-        except subprocess.CalledProcessError:
+        except (subprocess.CalledProcessError, FileNotFoundError):
+            # FileNotFoundError can arise when git is not installed
             git_branch = ""
 
         try:
@@ -63,7 +65,7 @@ def get_version_string(module):
                 .decode("ascii")
             )
             git_tag = "t=" + git_tag
-        except subprocess.CalledProcessError:
+        except (subprocess.CalledProcessError, FileNotFoundError):
             git_tag = ""
 
         try:
@@ -74,7 +76,7 @@ def get_version_string(module):
                 .strip()
                 .decode("ascii")
             )
-        except subprocess.CalledProcessError:
+        except (subprocess.CalledProcessError, FileNotFoundError):
             git_commit = ""
 
         try:
@@ -89,7 +91,7 @@ def get_version_string(module):
             )
 
             git_dirty = "dirty" if is_dirty else ""
-        except subprocess.CalledProcessError:
+        except (subprocess.CalledProcessError, FileNotFoundError):
             git_dirty = ""
 
         if git_branch or git_tag or git_commit or git_dirty: