private function setRequestUrl() {
    if ($this->tryGetOption(CURLOPT_URL, $value) && $value) {
      if (static::isSupportedUrlScheme($value, $scheme)) {
        $this->request->setUrl($value);
        return true;
      } else {
        $this->setError(CURLE_UNSUPPORTED_PROTOCOL,
                       sprintf("Unsupported protocol '%s'", $scheme));
      }
    } else {
      $this->setError(CURLE_URL_MALFORMAT, "No URL set!");
    }
    return false;
  }