Python OpenCV Cannot move to target thread 错误处理方法

$ cat /etc/lsb-release 
...
DISTRIB_DESCRIPTION="Ubuntu 18.04.5 LTS"
$ date
Tue Aug 11 11:43:16 KST 2020
$ python --version
Python 3.7.8
$ pip list|grep Qt
PyQt5                5.15.0
PyQt5-sip            12.8.0
$ pip list|grep opencv-python
opencv-python        4.3.0.38

# I downgraded opencv-python 4.3.0.38 to 4.3.0.36.

$ pip uninstall opencv-python
$ pip install opencv-python==4.3.0.36
$ pip list|grep opencv-python
opencv-python        4.3.0.36