code: public static String streamToString(InputStream inputStream, String fileName) {
          return streamToString(inputStream, fileName, null);
      }
docs: Copies UTF-8 input stream's content to a string (closes the stream).
  
  @param inputStream input stream (UTF-8) to read.
  @param fileName    description for stream in error messages.
  @return content of stream
  @throws RuntimeException if content could not be read.