__init__.py 文件源码

def load_transformers(name, config):
        transformers = []
        for version, names in six.iteritems(config):
            extension_manager = stevedore.ExtensionManager(
                'nailgun.cluster_upgrade.transformations.{}.{}'.format(
                    name, version),
                on_load_failure_callback=reraise_endpoint_load_failure,
            )
            try:
                sorted_extensions = [extension_manager[n].plugin
                                     for n in names]
            except KeyError as exc:
                LOG.error('%s transformer %s not found for version %s',
                          name, exc, version)
                raise
            strict_version = distutils.version.StrictVersion(version)
            transformers.append((strict_version, sorted_extensions))
        transformers.sort()
        return transformers