Set pbr 'warnerrors' option for doc build

By setting this pbr option in setup.cfg, the doc build will fail in case
of any warnings or errors occur during the build process. To be able to
turn on this setting, the current formatting errors were fixed.

Change-Id: Iec3f70eeb56c4652c2171e5f58c433f1434e6be1
Merge "Set pbr 'warnerrors' option for doc build"