Example of failure on master using widget_instance-master.patch:

haypo@selma$ ./python -m test -v -u all test_ttk_guionly 

======================================================================
ERROR: test_initialization (tkinter.test.test_ttk.test_extensions.LabeledScaleTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/haypo/prog/python/master/Lib/tkinter/test/test_ttk/test_extensions.py", line 14, in tearDown
    super().tearDown()
  File "/home/haypo/prog/python/master/Lib/tkinter/test/support.py", line 40, in tearDown
    w.destroy()
  File "/home/haypo/prog/python/master/Lib/tkinter/__init__.py", line 2305, in destroy
    % self.children)
Exception: destroy() doesn't clear all children: {'!labeledscale2': <tkinter.ttk.LabeledScale object .!frame.!labeledscale2>}


My https://github.com/python/cpython/pull/3025 PR fixes LabeledScale and OptionMenu destroy() method in the master branch.