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: I94aabb5b1ef43e8f0a5850620afce91ae0755e97

lower-constraints.txt

@@ -5,10 +5,8 @@ coverage==4.0
 debtcollector==1.2.0
 extras==1.0.0
 fixtures==3.0.0
-flake8==2.5.5
 gitdb==0.6.4
 GitPython==1.0.1
-hacking==0.12.0
 ipaddress===1.0.17
 iso8601==0.1.11
 keystoneauth1==3.4.0
@@ -23,8 +21,6 @@ oslo.i18n==3.15.3
 oslo.utils==3.33.0
 oslotest==3.2.0
 pbr==2.0.0
-pep8==1.5.7
-pyflakes==0.8.1
 pyparsing==2.1.0
 python-mimeparse==1.6.0
 python-subunit==1.0.0

test-requirements.txt

@@ -1,7 +1,7 @@
 # The order of packages is significant, because pip processes them in the order
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
-hacking>=1.1.0,<1.2.0 # Apache-2.0
+hacking>=3.0,<3.1.0 # Apache-2.0
 netaddr>=0.7.18 # BSD
 stestr>=2.0.0 # Apache-2.0
 

tox.ini

@@ -47,6 +47,7 @@ deps =
 
 [flake8]
 # E123, E125 skipped as they are invalid PEP-8.
+# W504 line break after binary operator
 show-source = True
-ignore = E123,E125
+ignore = E123,E125,W504
 exclude=.venv,.git,.tox,dist,doc,*lib/python*,*egg,build