code: protected String classifyWarning(final String message) {
          if (StringUtils.contains(message, "proprietary")) {
              return PROPRIETARY_API;
          }
          if (StringUtils.contains(message, "deprecated")) {
              return DEPRECATION;
          }
          return StringUtils.EMPTY;
      }
docs: Classifies the warning message: tries to guess a category from the
  warning message.
  
  @param message
  the message to check
  @return warning category, empty string if unknown