Sphinx >= 1.3 changes:
- Prototypes for init_values() requires a handle to warnings.warn
- New warning for setting the html_theme in conf.py to 'default':
sphinx.errors.SphinxWarning: WARNING: 'default' html theme has been
renamed to 'classic'. Please change your html_theme setting either
to the new 'alabaster' default theme, or to 'classic' to keep using
the old default.
This change deals with the above sphinx updates by adding the handle to
init_values() and setting pbr to _not_ fail on warnings when building the
docs.
Change-Id: Iba92628263e20efca84aeada0e19000f4c9b1fac
e19572e2d1