Implements Drupal\Core\Updater\UpdaterInterface::canUpdateDirectory().
Overrides UpdaterInterface::canUpdateDirectory
static function canUpdateDirectory($directory) {
  // This is a lousy test, but don't know how else to confirm it is a theme.
  if (file_scan_directory($directory, '/.*\\.module$/')) {
    return FALSE;
  }
  return TRUE;
}