Need to investigate these errors (happens rarely and usually after running threaded tests):

Traceback (most recent call last):
  File "C:\Users\Administrator\AppData\Local\Programs\Python\Python37\lib\tkinter\__init__.py", line 329, in __del__
    if self._tk.getboolean(self._tk.call("info", "exists", self._name)):
RuntimeError: main thread is not in main loop


 File "C:\Users\Administrator\AppData\Local\Programs\Python\Python37\lib\tkinter\__init__.py", line 1992, in wm_withdraw
    return self.tk.call('wm', 'withdraw', self._w)
_tkinter.TclError: bad window path name ".!toplevel17"