Comment 4 for bug 1864270

I had the same problem.
When I run sgt-launcher and try to start any game from it, I get error messages like Chris Guiver (guiverc):

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/sgtlauncher/SgtSocketLauncher.py", line 52, in callback
    withdrawn = self.wait_for_window_withdraw()
  File "/usr/lib/python3/dist-packages/sgtlauncher/SgtSocketLauncher.py", line 89, in wait_for_window_withdraw
    withdrawn = is_withdrawn(self.window_id)
  File "/usr/lib/python3/dist-packages/sgtlauncher/SgtSocketLauncher.py", line 178, in is_withdrawn
    withdrawn = not property_reply or property_value[0] == 0
TypeError: 'NoneType' object is not subscriptable

When I had upgraded to Ubuntu 20.04 by debian way (adding new repository and run aptitude), it stared to make error.
Then I tried command
apt-get dist-upgrade
as root, it finished successfully (it upgraded python2-minimal, python2 & libpython2-stdlib, which conflicts I was not able to solve with aptitude), but it does not help with sgt-launcher error, it still gives the same error.