Update hacking for Python3

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.

Remove hacking and friends from lower-constraints, they are not needed
to be installed at run-time.

Change-Id: Ia6af344ec8441dc98a0820176373dcff3a8c80d5

test-requirements.txt

@@ -5,7 +5,7 @@
 coverage>=4.5.1 # Apache-2.0
 doc8>=0.8.0 # Apache-2.0
 freezegun>=0.3.10 # Apache-2.0
-hacking>=1.1.0,<1.2.0 # Apache-2.0
+hacking>=3.0,<3.1.0 # Apache-2.0
 mock>=2.0.0 # BSD
 oslotest>=3.3.0 # Apache-2.0
 os-testr>=1.0.0 # Apache-2.0