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/graph.py

@@ -1,5 +1,13 @@
 from __future__ import print_function
 
+import argparse
+import cgi
+import datetime
+import json
+
+import pydot
+import urllib2
+
 # Copyright 2014-2016 OpenMarket Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
@@ -15,15 +23,6 @@ from __future__ import print_function
 # limitations under the License.
 
 
-import sqlite3
-import pydot
-import cgi
-import json
-import datetime
-import argparse
-import urllib2
-
-
 def make_name(pdu_id, origin):
     return "%s@%s" % (pdu_id, origin)
 
@@ -33,7 +32,7 @@ def make_graph(pdus, room, filename_prefix):
     node_map = {}
 
     origins = set()
-    colors = set(("red", "green", "blue", "yellow", "purple"))
+    colors = {"red", "green", "blue", "yellow", "purple"}
 
     for pdu in pdus:
         origins.add(pdu.get("origin"))
@@ -49,7 +48,7 @@ def make_graph(pdus, room, filename_prefix):
         try:
             c = colors.pop()
             color_map[o] = c
-        except:
+        except Exception:
             print("Run out of colours!")
             color_map[o] = "black"