pylint can or not resolve imports from the same package depending on whether files are specified or directories, and whether `-j 1` is set or not

[felixfontein]

When pylint runs in parallel, it seems to process paths to individual files differently from when -j 1 is set. Since with change detection we pass a list of individual files, this is a problem.

For exampe running ANTSIBULL_CHANGE_DETECTION=true nox -Re codeqa -v in the checkout of ansible-collections/community.docker#1155 results in the errors shown in CI, while nox -Re codeqa -v passes. I've traced the call chain back to:

1. pylint.lint.expand_modules() calls astroid.modutils.modpath_from_file()
2. astroid.modutils.modpath_from_file() calls astroid.interpreter._import.util.is_namespace()
3. astroid.interpreter._import.util.is_namespace() calls importlib.util._find_spec_from_path()
4. The latter returns different results depending on wether pylint is called with -j 1 or not.

The problem seems to be that _frozen_importlib_external.PathFinder.find_spec() returns None (without -j 1) vs. a proper spec (with -j 1) for ansible_collections. I've tried adding print() statements to my system's importlib version, but for some reason that doesn't result in anything.

[felixfontein]

(It seems that importlib is frozen and baked into the Python executable, so I won't be able to add print() statements to it without building Python myself...)

[felixfontein]

The default for pylint is to run serially, so this only happens if you explicitly tell it to run in parallel, for example by setting

[MAIN]
jobs=0

in the config file. (Which I happen to do...)

[felixfontein]

I finally got around to create a reproducer and reported this upstream: pylint-dev/pylint#10794