private void includeDisclaimer(File file, String disclaimer) throws ConfigException, IOException {
    String fileContent =
        FileUtils.readFileToString(file, brjs.bladerunnerConf().getDefaultFileCharacterEncoding());

    FileUtils.writeStringToFile(
        file, disclaimer + fileContent, brjs.bladerunnerConf().getDefaultFileCharacterEncoding());
  }
  @Override
  public void writeContent(ParsedContentPath contentPath, BundleSet bundleSet, OutputStream os)
      throws ContentProcessingException {
    // TODO not parse the config on every execution
    XmlBundlerConfig config = new XmlBundlerConfig(brjs);
    XmlBundleWriter bundleWriter = new XmlBundleWriter(config);
    List<Asset> xmlAssets = bundleSet.getResourceFiles(xmlAssetPlugin);

    try {
      String outputEncoding = brjs.bladerunnerConf().getBrowserCharacterEncoding();
      Writer output = new OutputStreamWriter(os, outputEncoding);

      if (config.isbundleConigAvailable()) {
        bundleWriter.writeBundle(xmlAssets, output);
      } else {
        bundleWriter.concatenateBundle(xmlAssets, output);
      }
      output.flush();
    } catch (IOException | ConfigException | XMLStreamException e) {
      throw new ContentProcessingException(e, "Error while processing XML assets '");
    }
  }