After the latest update on F9 a $ sudo revisor does not work. One has to $ sudo revisor --gui
It appears that GUI/CLI detection is broken. Maybe it's because I always launch revisor from the command line?
this should be solved in 2.1.1-4, pending updates at: https://admin.fedoraproject.org/updates/F9/pending/revisor-2.1.1-4.fc9