code: public void reportError (String message, Throwable cause) {
      errors.emit(new Error(message, cause));
      log().warn(message, cause);
    }
docs: Called when a backend (or other framework code) encounters an exception that it can recover
  from, but which it would like to report in some orderly fashion. <em>NOTE:</em> this method
  may be called from threads other than the main PlayN thread.