[work-in-progress] Test pytest vs python

Suggestion from https://github.com/pytest-dev/pytest/pull/11138#issuecomment-2088425080

With 'pytest' (launching the whole pylint test suite):
FAILED tests/test_precedence.py::test_package - AssertionError: E: 21: Module 'package.AudioTime' has no 'DECIMAL' member<function Equals.<locals>.<lambda> at 0x76c566741750>

With 'pytest tests/test_precedence.py':
tests/test_precedence.py .                                                                                                                                                                           [100%]

============================================================================================ 1 passed in 1.04s =============================================================================================

With 'python tests/test_precedence.py':
Checked ['package.__init__'] successfully
Checked ['precedence_test'] successfully
Checked ['import_package_subpackage_module'] successfully
Checked ['pylint.checkers.__init__'] successfully
Checked ['/home/pierre/pylint/tests/regrtest_data/classdoc_usage.py'] successfully
Checked ['/home/pierre/pylint/tests/regrtest_data/module_global.py'] successfully
Checked ['/home/pierre/pylint/tests/regrtest_data/decimal_inference.py'] successfully
Checked ['/home/pierre/pylint/tests/regrtest_data/absimp/string.py'] successfully
Checked ['/home/pierre/pylint/tests/regrtest_data/bad_package'] successfully
1 file changed