code: private static String getTopLevelCauseMessage(Throwable t) {
          Throwable topLevelCause = t;
          while (topLevelCause.getCause() != null) {
              topLevelCause = topLevelCause.getCause();
          }
          return topLevelCause.getMessage();
      }
docs: Returns the Message attached to the original Cause of |t|.