gistfile1.txt

.retryWhen(errors -> errors.flatMap(error -> {
              // For IOExceptions, we  retry
              if (error instanceof RetrofitError) {
                RetrofitError retrofitError = (RetrofitError) error;
                Response response = retrofitError.getResponse();
                if (response.getStatus() == 504) {
                  return Observable.just(null);
                }
              }
              // For anything else, don't retry
              return Observable.error(error);
            })
        )