`atexit` module breaks refleak check

Bug report

Bug description:

If the test registers a callback with atexit module, refleak test will consider it a leak.

    def test_refleak(self):
        atexit.register(lambda: None)

This is the root cause of the buildbot failure of https://github.com/python/cpython/pull/139185. It's a couple of coincidences that caused the seemingly unrelated issue. Basically, clearing the module cache in test_zipimport made the module-level code in rlcompleter, which includes a register to atexit, run more than once.

There are a few possible approaches to fix this, but I did not find the solution that I'm immediately happy with.

I consider this a test framework bug as this should be a valid behavior. The ideal solution is to keep the atexit callbacks before running test in a loop and restore it after. However, atexit does not provide such an interface, public or private. You can either clear it or run it. The callbacks are stored in a state of the interpreter and we don't have any access to it.

Without that, we either need to somehow calculate the allocated memory by atexit, or hope that no one writes a test that writes to atexit. Of course there might be other ways that I did not think of.

CPython versions tested on:

CPython main branch

Operating systems tested on:

macOS

Linked PRs

• gh-139305
• gh-139357

• [3.14] gh-139305 was backported as part of gh-139280

Comienza con el framework de pruebas refleak y el ejemplo test_refleak que registra un callback de atexit. Inspecciona cómo el borrado de la caché de módulos por parte de test_zipimport hace que el registro a nivel de módulo de rlcompleter se ejecute repetidamente, y revisa los PRs vinculados gh-139305 y gh-139357 para consultar el trabajo existente. Se considera terminado cuando los registros válidos de atexit ya no aparecen como refleaks.