Hi. Over at python-pillow/Pillow#4769, we've started receiving an error in Python 3.9 -

TypeError: exec_module() missing 1 required positional argument: 'module'

I find that our code passes with setuptools 47.3.1, but fails with 47.3.2. Investigating, I find that https://github.com/pypa/setuptools/pull/2071/files adds ExtensionFileLoader(__name__,__file__).exec_module() - calling exec_module without any arguments.

Looking at https://docs.python.org/3/library/importlib.html#importlib.machinery.ExtensionFileLoader, I would conclude that yes, exec_module does require an argument.

I'm hoping that seems like a suitably obvious bug in setuptools. Let me know if it's not.