Running tests with package installed yields ResourceWarnings

[FriedrichFroebel]

I am currently working on a tests refactoring of one of the packages I maintain (didjvu) and stumbled upon some ResourceWarnings popping up, which seem to originate from vext (the following one is only one example - the same happens for some .py files as well):

<frozen importlib._bootstrap_external>:1359: ResourceWarning: unclosed file <_io.BufferedReader name='/home/me/github/jwilk/env/lib/python3.8/site-packages/gamera/plugins/_runlength.cpython-38-x86_64-linux-gnu.so'>
Object allocated at (most recent call last):
  File "<frozen importlib._bootstrap>", lineno 219
  File "/home/me/github/jwilk/env/lib/python3.8/site-packages/gamera/plugins/runlength.py", lineno 22
    import _runlength
  File "<frozen importlib._bootstrap>", lineno 991
  File "<frozen importlib._bootstrap>", lineno 971
  File "<frozen importlib._bootstrap>", lineno 914
  File "<frozen importlib._bootstrap_external>", lineno 1407
  File "<frozen importlib._bootstrap_external>", lineno 1381
  File "<frozen importlib._bootstrap_external>", lineno 1359
  File "/home/me/github/jwilk/env/lib/python3.8/site-packages/vext/gatekeeper/__init__.py", lineno 253
    module_info = imp.find_module(fullname, [other_path])
  File "/usr/lib/python3.8/imp.py", lineno 302
    file = open(file_path, mode, encoding=encoding)

I am using vext for vext.gi to be available, although the aforementioned code should not actually use any gi imports in theory.

Command: python3 -m unittest discover --start-directory tests/.

For tracing the calls, I enclosed the corresponding test method into

import tracemalloc
tracemalloc.start(10)
...
tracemalloc.stop()

[FriedrichFroebel]

This probably becomes obsolete once the deprecated imp usages have been replaced. Python 3.12, published three months ago, completely removed imp from the stdlib.