Comment 7 for bug 1472503

Closing in keystone based on comment #5. The version constraint for pbr in keystone's requirements already includes the latest version, but the minimum could certainly be bumped OpenStack-wide:

  https://github.com/openstack/keystone/blob/7efc3d/requirements.txt#L5

  https://github.com/openstack/requirements/blob/7f192f/global-requirements.txt#L105