Run mypy in pre-commit, through a pyenv/virtualenv enabler wrapper script

[scop]

Description:

I believe this would fix the issues we're having and kind of poorly working around with mypy needing our venv active but it might not be, e.g. when committing from a GUI tool not launched from a venv-activated shell. Supports pyenv(-virtualenv) and venvs in a couple of typical dirs, falls back gracefullly if no venv found.

Related issue (if applicable): fixes #

Pull request with documentation for home-assistant.io (if applicable): home-assistant/home-assistant.io#<home-assistant.io PR number goes here>

Example entry for configuration.yaml (if applicable):

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in home-assistant.io

If the code communicates with devices, web services, or third-party tools:

• The manifest file has all fields filled out correctly. Update and include derived files by running python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt by running python3 -m script.gen_requirements_all.
• Untested files have been added to .coveragerc.

If the code does not interact with devices:

• Tests have been added to verify that the new code works.

[scop]

@balloob would you happen to have time to check this out? I'm not aware of anything I've missed, and I think we could just try it out and see if folks run into any issues. The virtualenvs must be either managed by pyenv-virtualenv, or be located in venv/ or .venv/ but I think that's a reasonable assumption an could be extended.

In addition to getting more mypy coverage on dev systems, we'd avoid problems when people are forgetting to address the -all config when making pre-commit changes; we're already seeing that with some smaller changes, addition of codespell etc.

[balloob]

I run my venv in root of repo. So am I supported?

[balloob]

Ah see that case is covered. Looks good

[scop]

Thanks!