Comment 11 for bug 1379998

Change abandoned by Thomas Bechtold (<email address hidden>) on branch: master
Review: https://review.openstack.org/193462
Reason: Fixed by http://git.openstack.org/cgit/openstack-dev/pbr/commit/?id=e19572e2d10107ad316d81f90a4310268faac387 .

But without tests and warnings disabled. Anyway - at least newer Sphinx versions are working now.