Start using Pyflakes and Hacking

Instead of globally ignoring pyflakes and
hacking warnings, only blacklist those that trigger
very frequently so far, in order to clean them
up in followup commits. Fix and start gating
on the rest already.

Change-Id: Ied7c7250061e3bf379e8286e8ce3b9e4af817faf

tests/test_http.py

@@ -61,7 +61,7 @@ class TestClient(testtools.TestCase):
             # rather than assertRaises() so that we can check the body of
             # the exception.
             self.fail('An exception should have bypassed this line.')
-        except exc.CommunicationError as comm_err:
+        except glanceclient.exc.CommunicationError as comm_err:
             fail_msg = ("Exception message '%s' should contain '%s'" %
                        (comm_err.message, self.endpoint))
             self.assertTrue(self.endpoint in comm_err.message, fail_msg)