Fix namespace package detection for frozen stdlib modules on PyPy

[jacobtylerwalls]

Description

PyPy doesn't bother to set __spec__ on some frozen stdlib modules like importlib._bootstrap. We were using the lack of __spec__ as a heuristic for old-style namespace packages with pkg_resources. That assumption breaks given PyPy's behavior.

Type of Changes

	Type
✓	🐛 Bug fix

Related Issue

Fixes #1755

[coveralls]

Pull Request Test Coverage Report for Build 2940401201

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.0007%) to 92.347%

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Totals
Change from base Build 2925757434:	0.0007%
Covered Lines:	9714
Relevant Lines:	10519

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💛 - Coveralls

[Pierre-Sassoulas]

LGTM but I don't have pypy installed, let's wait for the reporter to confirm it works.

[emcd]

@jacobtylerwalls : It works both against the minimal reproducer and the use case that originally triggered the issue. Thank you!

[DanielNoord]

Note to self: I actually opened an issue against PyPy for this. I'll open a PR to add some reference to this as I think it would be good to link it.

Also, shouldn't we try to infer namespaces better on PyPy? Instead of just giving up?

[jacobtylerwalls]

I actually opened an issue against PyPy for this.

Thank you!

Also, shouldn't we try to infer namespaces better on PyPy? Instead of just giving up?

Only old-style pkg_resources namespace packages were affected, so I wasn't very concerned. We ought to quickly backport a crash fix, was my thinking.