Fatal Python error: PyEval_RestoreThread: the function must be called with the GIL held, but the GIL is released (the current Python thread state is NULL)

[frakman1]

Bug Report

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Context

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When I click on a button that launches a thread/function:

app.setCheckBoxChangeFunction(FOLLOW_DESKTOP, followDesktopPressed)

... a call to an open-cv function within that function like cv2.namedWindow(... ) results in this error:

Fatal Python error: PyEval_RestoreThread: the function must be called with the GIL held, but the GIL is released (the current Python thread state is NULL)
Python runtime state: initialized

Current thread 0x00007fff9792c380 (most recent call first):
  File "/Users/frak/git/myAppJar/virtualenv/lifx-lan-gui/lights.py", line 1010 in followDesktopPressed
  File "/usr/local/lib/python3.9/site-packages/appJar/appjar.py", line 3783 in <lambda>
  File "/usr/local/Cellar/python@3.9/3.9.9/Frameworks/Python.framework/Versions/3.9/lib/python3.9/tkinter/__init__.py", line 1892 in __call__
  File "/usr/local/Cellar/python@3.9/3.9.9/Frameworks/Python.framework/Versions/3.9/lib/python3.9/tkinter/__init__.py", line 1429 in mainloop
  File "/usr/local/lib/python3.9/site-packages/appJar/appjar.py", line 1886 in go
  File "/Users/frak/git/myAppJar/virtualenv/lifx-lan-gui/lights.py", line 1593 in <module>
Abort trap: 6

Expected Behaviour

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This used to work in a previous version of python (3.7 maybe) with no errors
I am currently using python 3.9.9 on Mac OS High Sierra

Version Information

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Replace this with the result of running your code with the -v flag: python myCode.py -v

appJar: 0.94.0 Python: 3.9.9 TCL: 8.6, TK: 8.6 Platform: Darwin pid: 69923 locale: en_US