Add ament_lint_auto_py and ament_lint_common_py

[InvincibleRMC]

Description

Adding ament_lint_auto_py and ament_lint_common_py to allow auto linting for ament_python packages. It should have 1 to 1 parity with ament_lint_auto features. Including support for ament_lint_auto_exclude and ament_lint_auto_file_exclude.

Is this user-facing behavior change?

Yes it would simpler running linters in ament_python build packages. Throughout the core sometimes linters get missed. And if we ever wanted to add more in the future [like ament_mypy for typing ;)] being able to use similar logic to ament_lint_auto in CMakeLists.txt would be very useful.

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Additional Information

[peci1]

I very much like this initiative.

Does it mean that all the copy-pasted lint tests in downstream repos would be replaced just by something like test_ament_lint_auto.py from the readme? Is there no way to do it even without this one (e.g. generate it at build time)?

It's not clear to me why does ament_lint_common_py contain also the C++-only linters like cppcheck. Does it make sense in some scenarios? Or is it just to have 1:1 mapping between cpp and py linters? Regardless of the answer, I think this should be documented in the readme.

Also, setting excludes only via environment variables is insufficient. That's good for local development, but unusable on the buildfarm and in other automated build environments. Or am I missing something?

If specifying the excludes in setup.py is not possible, what about the export section in package.xml? But I don't like this solution either because it would leak implementation details like file names leak into the overall metadata provided by package.xml.

[InvincibleRMC]

Do to your questions/feedback I have done some updates.

1. I was able to remove needing the def test_ament_lint_auto() function from being called downstream now just having ament_lint_auto_py in the package.xml will cause all linters listed in the package.xml to run.
2. Added a note about keeping parity between ament_lint_common and ament_lint_common_py. I could see a world we remove the C++ lint dependencies but, the initial implementation goal was parity.
3. For settings I moved from environment variables to pytest variables to be configured in a pytest.ini /pyproject.toml per package.

[InvincibleRMC]

@fujitatomoya would you mind reviewing this?

[fujitatomoya]

i got several minor comments only, i would like someone else who is familiar with ament to review this before merge.