six.py SystemError in frozen apps that embed PySide2

When embedding PySide2 5.12.1 using either PyInstaller, py2app, or cx_freeze in a frozen executable, the app crashes right after opening.

The traceback points to six.py, specifically: 

File "six.pyc", line 318, in <module>
  moves = _MovedItems(__name__ + ".moves")
File "six.pyc", line 128, in __init__
  self.__doc__ = self.__class__.__doc__
SystemError: <method-wrapper '__get__' of getset_descriptor object at 0x100072bd0> returned a result with an error set

This error does not show up if the same codebase is executed from sources.

This issue has been experienced by other developers and reported on the PyInstaller (link) and six.py (link) trackers.

So far, we have reports of this issue on Windows and macOS. with Python 3.6 and 3.7.