tnx for your comment.
Alas I think python-wxgtk2.8 cannot solve the problem for me.
On https://packages.ubuntu.com/xenial/otherosfs/playonlinux there´s the info that python-wxgtk3.0 only is needed for my system and that´s installed.
Besides: On bodhilinux in my VM there´s no python-wxgtk2.8 either, just python-wxgtk3.0. And it works there.