'Raise for non-default faulty extensions.
Gracefully fail for defective default extensions, which will be
removed from the list of loaded extensions.'

def _check_faulty_extensions(self, faulty_extensions):

    default_extensions = set(const.DEFAULT_SERVICE_PLUGINS.values())
    if (not (faulty_extensions <= default_extensions)):
        raise exceptions.ExtensionsNotFound(extensions=list(faulty_extensions))
    else:
        for ext in faulty_extensions:
            try:
                del self.extensions[ext]
            except KeyError:
                pass
