(originally filed as https://bugzilla.suse.com/1193409)

When trying to start "idle3.8", I get a ZeroDivisionError in
editor.py. Trying to patch it, I noticed that the complete UI of
IDLE shows no text. Since the same also happens with "idle3.9",
I guess it is a bug in tk.

The error happens also with a fresh user account.

The complete error message is as follows:

> idle3.8
Traceback (most recent call last):
  File "/usr/bin/idle3.8", line 5, in <module>
    main()
  File "/usr/lib64/python3.8/idlelib/pyshell.py", line 1522, in main
    shell = flist.open_shell()
  File "/usr/lib64/python3.8/idlelib/pyshell.py", line 329, in open_shell
    self.pyshell = PyShell(self)
  File "/usr/lib64/python3.8/idlelib/pyshell.py", line 874, in __init__
    OutputWindow.__init__(self, flist, None, None)
  File "/usr/lib64/python3.8/idlelib/outwin.py", line 79, in __init__
    EditorWindow.__init__(self, *args)
  File "/usr/lib64/python3.8/idlelib/editor.py", line 218, in __init__
    self.set_width()
  File "/usr/lib64/python3.8/idlelib/editor.py", line 366, in set_width
    self.width = pixel_width // zero_char_width
ZeroDivisionError: integer division or modulo by zero
>