Sync up with global requirements

This is a pull from openstack/requirements.

Note that pep8, pyflakes and flake8 are now specified
as deps in hacking, so we can remove those here.  Also
if we don't remove them then we run into version conflicts
when hacking tries to set things up.

Quick!!!  Before it changes again!

Change-Id: Ib35b58c01f8d5d066d559e8afe4ea02adf55db5d
Merge "Sync up with global requirements"