Issue #3221507 by mxr576: mkdir can fail in...

    // Only write when necessary.

    if (!file_exists($full_path) || md5_file($full_path) !== md5($altered_code)) {

      // Create directory when necessary.

      if (!file_exists($directory)) {

        mkdir($directory, 0777, TRUE);

      if (!is_dir($directory) && !@mkdir($directory, 0777, TRUE) && !is_dir($directory)) {

        throw new \RuntimeException('Unable to create directory: ' . $directory);

      }

      file_put_contents($full_path, $altered_code);

    }