tests fail when git python module isn't installed

[paper42]

Bug description

Run pytest without having the git python module installed, they will fail on import git:

https://github.com/PyCQA/pylint/blob/5e9d20dc32768e873ab84bc4ed0b489fdda40672/pylint/testutils/primer.py#L1-L10

cc @Pierre-Sassoulas

Configuration

No response

Command used

pytest

Pylint output

-

Expected behavior

Tests which require git python module are skipped on systems without this module.

Pylint version

pylint 2.12.2
astroid 2.9.0
Python 3.10.0 (default, Oct 25 2021, 19:14:18) [GCC 10.2.1 20201203]

OS / Environment

No response

Additional dependencies

No response

[Pierre-Sassoulas]

We added git python to the tests requirements when we added primer, but they are indeed used in pylint.testutils. So they should be a pylint runtime dependency.

I'd hate to do that though, most user do not need testutils and only use pylint as a linter a not as a lib that they extend.

I think we could create a separate package pylint-testutils so it does not pollute pylint's dependencies. Another advantage would be that we can do major when we break something in pylint.testutil instead of what we're doing right now (consider that it's not a public API). What do you think @DanielNoord @cdce8p ?

[cdce8p]

So they should be a pylint runtime dependency.

pylint.testutils isn't a runtime dependency. It works just fine for Home-Assistant. Only if you want to use the pylint test interface is it required.

A separate package is a lot of work even if we automate most of it. I would suggest extras_require for it. Users could then do install it like this. (We can obviously change the name.)

pip install pylint[test-lib]

https://setuptools.pypa.io/en/latest/userguide/dependency_management.html#optional-dependencies

[Pierre-Sassoulas]

pip install pylint[testutil] does sound like the best of both world, I like that.