Fix PyreverseConfig imports in pyreverse's tests

[Pierre-Sassoulas]

Type of Changes

	Type
✓	🐛 Bug fix

Description

Fix an import error due to pytest adding all file to the pythonpath before launching tests.

[Pierre-Sassoulas]

@DudeNr33 fyi, I just realized that pytest is adding all file to the pythonpath so the tests were working but not pylint or mypy :)

[coveralls]

Pull Request Test Coverage Report for Build 1236529571

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 93.075%

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Totals
Change from base Build 1235242213:	0.0%
Covered Lines:	13253
Relevant Lines:	14239

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💛 - Coveralls

[DanielNoord]

I don't actually think this fully solved the issue. My IDE can no longer detect PyreverseConfig and Pylance also complains about this. See screenshots below.
At some point mypy is going to complain about this. I would be in favour of reversing this commit.

Without this commit:

[Pierre-Sassoulas]

How about we move this class to pylint.pyreverse? It seems it's an interface for optparse.Config that might help with typing for pylint's code too.

[DudeNr33]

No, not really - the "real" config class comes from the pylint.config.configuration_mixin.ConfigurationMixin, from which pylint.pyreverse.main.Run inherits from.
This is just a simplified helper class that represents the config for the tests.
However, we could move it to pylint.testutils.

[DanielNoord]

This is actually preventing me from running the test suite locally. I get:

../../../../.pyenv/versions/3.9.6/lib/python3.9/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
tests/pyreverse/test_writer.py:31: in <module>
    from tests.pyreverse.conftest import PyreverseConfig
E   ModuleNotFoundError: No module named 'tests'

with tox --recreate -e py39 .