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

1 files changed, 4 insertions, 5 deletions

diff --git a/synapse/metrics/background_process_metrics.py b/synapse/metrics/background_process_metrics.py
index 70e0fa45d9..b56986d8e7 100644
--- a/synapse/metrics/background_process_metrics.py
+++ b/synapse/metrics/background_process_metrics.py
@@ -208,7 +208,8 @@ def run_as_background_process(desc: str, func, *args, bg_start_span=True, **kwar
                     return await maybe_awaitable(func(*args, **kwargs))
             except Exception:
                 logger.exception(
-                    "Background process '%s' threw an exception", desc,
+                    "Background process '%s' threw an exception",
+                    desc,
                 )
             finally:
                 _background_process_in_flight_count.labels(desc).dec()
@@ -249,8 +250,7 @@ class BackgroundProcessLoggingContext(LoggingContext):
         self._proc = _BackgroundProcess(name, self)
 
     def start(self, rusage: "Optional[resource._RUsage]"):
-        """Log context has started running (again).
-        """
+        """Log context has started running (again)."""
 
         super().start(rusage)
 
@@ -261,8 +261,7 @@ class BackgroundProcessLoggingContext(LoggingContext):
             _background_processes_active_since_last_scrape.add(self._proc)
 
     def __exit__(self, type, value, traceback) -> None:
-        """Log context has finished.
-        """
+        """Log context has finished."""
 
         super().__exit__(type, value, traceback)