code: protected void setErrorMessageInCookie(final HttpServletResponse response,
        final String errorMsg) {
      final Cookie cookie = new Cookie(AZKABAN_FAILURE_MESSAGE, errorMsg);
      cookie.setPath("/");
      response.addCookie(cookie);
    }
docs: Sets an error message in azkaban.failure.message in the cookie. This will be used by the web
  client javascript to somehow display the message