With pbr 2.0 and Sphinx 1.5, the setting for treat sphinx warnings as
errors is setting warning-is-error in build_sphinx section. Migrate the
setting from the old warnerrors one.
There are two issues:
- The `*` character is recognized as an emphasis character and must be
escaped
- The index references modules that have since been removed
These are resolved.
Change-Id: Id078022c0f75bf8f162b693d260f67116eb6428b
6e04f882c4