Use Sphinx 1.5 warning-is-error
Use Sphinx 1.5 warning-is-error

This will ensure doc warnings don't make their way in.

Change-Id: I9a007ad89f3a2219feb960fee858bf70c1643416

dtroyer/python-openstackclient,dtroyer/python-openstackclient,openstack/python-openstackclient,openstack/python-openstackclient