Update hacking for Python3

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

Fix problems found.

Change-Id: I5d2ab99725e97437b8dc3dc805c79b4a14610d6c

test-requirements.txt

@@ -1 +1 @@
-hacking<0.11,>=0.10.0
+hacking>=3.0,<3.1.0 # Apache-2.0

tox.ini

@@ -20,6 +20,7 @@ commands = {posargs}
 
 [flake8]
 # E125 and H are intentionally ignored
-ignore = E125,H
+# W504 line break after binary operator
+ignore = E125,H,W504
 show-source = True
 exclude = .venv,.tox,dist,doc,build,*.egg