Python 3 imports may fail if a Python 2 .pyc file exists without an accompanying .py file.

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My project vendors code, and we recently updated "requests" to a drastically newer version.

As part of this version change, `requests/packages/__init__.py` was removed, and  `requests/packages.py` was added.

This project is long-lived, and many people have imported `requests` with Python 2. So, `requests/packages/__init__.pyc` exists.

After making this update, importing requests with Python 3 fails:
`ImportError: bad magic number in 'parent.child': b'\x03\xf3\r\n'`

Interestingly, deleting `requests/packages/__init__.pyc` allows Python 3 to work again.

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I've attached a "reproduction" script that produces the directory structure and tweak required to cause the failure.
I'm running Python 2.7.18 and Python 3.9.1.

Looking closer into this, it appears that Python 3 will still try to load non-__pycache__ `.pyc` files. Perhaps I'm missing context, but aren't those only supposed by to written and read by Python 2?

Location where `pyc` loader is registered: https://github.com/python/cpython/blob/v3.9.4/Lib/importlib/_bootstrap_external.py#L1571-L1572
Location where `__pycache__` loading happens is part of SourceFileLoader here: https://github.com/python/cpython/blob/v3.9.4/Lib/importlib/_bootstrap_external.py#L870

I'll attach a patch to remove this pyc-loading for convenience, but I don't have enough context to be confident that it's the correct solution.

Unless you find documentation that says otherwise, this an enhancement proposal for 3.11.

If no core developer (other than me) jumps on this, you might use git blame to fine out who committed code in the area you proposed changing.

I'm going to close this here - I currently don't have the cycles to push this forward. Besides, this issue only occurs in environments that are using both Python 2 and 3, and as Python 2's EOL date gets further in the past, the severity of this ticket decreases.

For future readers, if you need a workaround for this exact problem, it was solved by my team with this import hook: https://hg.mozilla.org/mozilla-central/file/50e4a4e6975a7f828277a2b9c3cc9770a6c94107/build/mach_initialize.py#l630