cli: check message command addition

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
cli: fix check message command test

* Removes the check from Python 3.

Signed-off-by: Yoan Blanc <yoan.blanc@cern.ch>
cli: tests refactoring

Signed-off-by: Yoan Blanc <yoan.blanc@cern.ch>