Bug#923465: Freecad - No module named StartGui

[John Lines]

I had this message after I removed libfreecad-python2-0.17 which was
preventing my updated freecad from running properly

I then did
  apt-get install freecad-python3 

I got the message

Setting up python3-pyside2.qtopengl (5.11.2-3) ...
Setting up libfreecad-python3-0.18 (0.18~pre1+dfsg1-4) ...
Setting up python3-pivy (0.6.4-1) ...
Setting up freecad-python3 (0.18~pre1+dfsg1-4) ...
update-alternatives: warning: forcing reinstallation of alternative
/usr/lib/freecad/bin/freecad-python2 because link group freecad is
broken

but my system now seems to be working - I suggest trying doing an
update-alternatives to force freecad-python2 to be used properly