public static function deleteImageServingUrl($gs_filename) {
    $blob_key = self::createGsKey($gs_filename);
    $req = new ImagesDeleteUrlBaseRequest();
    $resp = new ImagesDeleteUrlBaseResponse();
    $req->setBlobKey($blob_key);

    try {
      ApiProxy::makeSyncCall('images',
                             'DeleteUrlBase',
                             $req,
                             $resp);
    } catch (ApplicationError $e) {
      throw self::imagesApplicationErrorToException($e);
    }
  }