Lint the contrib/ directory in CI and linting scripts, add synctl to linting script (#7914)

Run `isort`, `flake8` and `black` over the `contrib/` directory and `synctl` script. The latter was already being done in CI, but now the linting script does it too.

Fixes https://github.com/matrix-org/synapse/issues/7910

contrib/graph/graph3.py

@@ -1,5 +1,15 @@
 from __future__ import print_function
 
+import argparse
+import cgi
+import datetime
+
+import pydot
+import simplejson as json
+
+from synapse.events import FrozenEvent
+from synapse.util.frozenutils import unfreeze
+
 # Copyright 2016 OpenMarket Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
@@ -15,16 +25,6 @@ from __future__ import print_function
 # limitations under the License.
 
 
-import pydot
-import cgi
-import simplejson as json
-import datetime
-import argparse
-
-from synapse.events import FrozenEvent
-from synapse.util.frozenutils import unfreeze
-
-
 def make_graph(file_name, room_id, file_prefix, limit):
     print("Reading lines")
     with open(file_name) as f:
@@ -106,7 +106,7 @@ def make_graph(file_name, room_id, file_prefix, limit):
         for prev_id, _ in event.prev_events:
             try:
                 end_node = node_map[prev_id]
-            except:
+            except Exception:
                 end_node = pydot.Node(name=prev_id, label="<<b>%s</b>>" % (prev_id,))
 
                 node_map[prev_id] = end_node