'Build docs with additional doc backends
These steps are not necessarily required for the build to halt, so we
only raise a warning exception here. A hard error will halt the build
process.'

def build_docs_class(self, builder_class):

    builder = get_builder_class(builder_class)(self.build_env, python_env=self.python_env)
    success = builder.build()
    builder.move()
    return success
