code: public void error(Object message, Throwable t)
      {
          if (IS12)
          {
              getLogger().log(FQCN, Level.ERROR, message, t);
          }
          else
          {
              getLogger().log(FQCN, Level.ERROR, message, t);
          }
      }
docs: Log an error to the Log4j Logger with <code>ERROR</code> priority.