Update hacking for Python3

The repo is Python 3 now, so update hacking to version 3.0 which
supports Python 3.

Fix problems found.

Remove hacking and friends from lower-constraints, they are not needed
for installation.

Change-Id: I5ae47a7b11ff29a301e440c15daf30db7738485b

tox.ini

@@ -63,7 +63,8 @@ commands =
 
 [flake8]
 # E731 skipped as assign a lambda expression
-ignore = E731,F403,F812,F821
+# W504 line break after binary operator
+ignore = E731,F403,F812,F821,W504
 show-source = True
 exclude = .venv*,.tox,dist,*egg,build,.git,doc,*lib/python*,.update-venv