protected function setMultisiteFilePermissions($perms) {
    $taskFilesystemStack = $this->taskFilesystemStack();
    $multisites = $this->getConfigValue('multisites');
    foreach ($multisites as $multisite) {
      $multisite_dir = $this->getConfigValue('docroot') . '/sites/' . $multisite;
      $taskFilesystemStack->chmod($multisite_dir, $perms);
    }
    $taskFilesystemStack->setVerbosityThreshold(VerbosityThresholdInterface::VERBOSITY_VERBOSE);
    $taskFilesystemStack->run();
  }