This repo is now testing only with Python 3, so let's make
a few cleanups:
- Remove now unused files babel.cfg and openstack-common.conf.
- Remove use of six library.
- Update to hacking 3.1.0
- Update pbr requirement
Change-Id: Ib4b9460f24cfaa216f0302b3b90ef73d808eb3e4
In preparation for python 3 support switch to newer sphinx version.
This requires openstackdocstheme.
Remove install_command, this is the default.
Update hacking version to be compatible with python 3, fix warnings
from new pep8.
Change-Id: Iab69ec59eb111571f784242c5ea5756c2a63e424