The repo is Python 3 now, so update hacking to version 3.0 which
supports Python 3.
Fix problems found.
Update local hacking checks for new flake8.
Note: The repo has been using an uncapped requirements, so was testing with
hacking 2.0 which disabled the old way of local testing integration.
Remove S367 and S368 since they are not working under python3
"NOTE(Kezar): This checks a good enough if we have only py2.7 supported.
As soon as we'll get py3.x we need to drop it or rewrite. You can read more
about it in dev-list archive, topic: "[hacking]proposed rules drop for 1.0"
Also, hacking now has H304 and H306 which test exactly the same.
Remove hacking and friends from lower-constraints, it's not needed
there.
Change-Id: If60682fb328359ef73dee8f2d89d51410a376677
cca4f4d0c8