public function isDrupalInstalled() {
    $this->logger->debug("Verifying that Drupal is installed...");
    $result = $this->executor->drush("sqlq \"SHOW TABLES LIKE 'config'\"")->run();
    $output = trim($result->getMessage());
    $installed = $result->wasSuccessful() && $output == 'config';

    return $installed;
  }