Add hacking to requirements

Solely for the transitive dependencies.  Ignore errors from hacking
as do the other openstack-infra python projects.

Change-Id: Ib5953c31a5380f9f57c7f79e1ce0699aef5eb629

test-requirements.txt

@@ -1,3 +1,4 @@
+hacking>=0.5.6,<0.8
 discover
 fixtures
 python-subunit

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 minversion = 1.6
-envlist = pep8, pyflakes, py26, py27
+envlist = pep8, py26, py27
 
 [tox:jenkins]
 downloadcache = ~/cache/pip
@@ -16,8 +16,7 @@ deps = -r{toxinidir}/requirements.txt
 commands = python setup.py testr --slowest --testr-args='{posargs}'
 
 [testenv:pep8]
-deps = pep8==1.3.3
-commands = pep8 --repeat --show-source --ignore=E125 --exclude=.venv,.tox,dist,doc,build,*egg . {posargs}
+commands = flake8
 
 [testenv:pyflakes]
 deps = pyflakes
@@ -34,3 +33,10 @@ commands = python setup.py build_sphinx
 
 [testenv:venv]
 commands = {posargs}
+
+[flake8]
+# These are ignored intentionally in openstack-infra projects; please
+# don't submit patches that solely correct them or enable them.
+ignore = E125,H
+show-source = True
+exclude = .venv,.tox,dist,doc,build,*.egg