Implements Drupal\Core\FileTransfer\FileTransfer::createDirectoryJailed().
Overrides FileTransfer::createDirectoryJailed
protected function createDirectoryJailed($directory) {
  if (@(!ssh2_exec($this->connection, 'mkdir ' . escapeshellarg($directory)))) {
    throw new FileTransferException('Cannot create directory @directory.', NULL, array(
      '@directory' => $directory,
    ));
  }
}