Clean up a lot of pyflakes warnings (#1153)

Clean up unused imports or unused variables to mostly silence pyflakes.
We aren't quite yet in a place where we can run it via Travis, but baby
steps.

github/Requester.py

@@ -325,7 +325,7 @@ class Requester:
                 data = data.decode("utf-8")  # pragma no cover (Covered by Issue142.testDecodeJson with Python 3)
             try:
                 return json.loads(data)
-            except ValueError, e:
+            except ValueError:
                 return {'data': data}
 
     def requestJson(self, verb, url, parameters=None, headers=None, input=None, cnx=None):