A few minutes after posting the aforementioned problem, I tried to copy an older version of pycupsmodule.so (extracted from printconf-gui 0.6.151-1 rpm) and this seemed to have solved the problem (further testing needed, though).
So, is the newer pycupsmodule.so somehow corrupted (I have also tried to reinstall printconf-gui 0.6.151.7-1 but the problem persisted)?
Regards,
Iwan