fix: Downgraded yamllint as v1.38.0 dropped support for Python 3.9

[abhishekmadan30]

https://pypi.org/project/yamllint/1.38.0/

[jcristau]

Why/where do we need to run yamllint with python 3.9?

[abhishekmadan30]

I was trying to submit a PR to taskgraph, and this is the error you get if you still have yamllint set to v138:

$ git commit --amend
[INFO] Installing environment for https://github.com/adrienverge/yamllint.git.
[INFO] Once installed this environment will be reused.
[INFO] This may take a few minutes...
An unexpected error has occurred: CalledProcessError:
  command: ('/Users/amadan/.cache/pre-commit/repoxwxw9nmo/py_env-python3/bin/python', '-mpip', 'install', '.')
  return code: 1
  stdout:
    Processing /Users/amadan/.cache/pre-commit/repoxwxw9nmo
      Installing build dependencies: started
      Installing build dependencies: finished with status 'done'
      Getting requirements to build wheel: started
      Getting requirements to build wheel: finished with status 'done'
      Preparing metadata (pyproject.toml): started
      Preparing metadata (pyproject.toml): finished with status 'done'
    INFO: pip is looking at multiple versions of yamllint to determine which version is compatible with other requirements. This could take a while.
  stderr:
    ERROR: Package 'yamllint' requires a different Python: 3.9.6 not in '>=3.10'
Check the log at /Users/amadan/.cache/pre-commit/pre-commit.log

[jcristau]

That sounds like a local problem on your end?

[abhishekmadan30]

I don't think so (not a 100% sure) as I don't even have Python 3.9 on my machine. Are you able to commit to taskgraph without getting this precommit error ?

[jcristau]

What's /Users/amadan/.cache/pre-commit/repoxwxw9nmo/py_env-python3/bin/python?

[ahal]

Yeah it works for me. It means however you installed pre-commit, it's using Python 3.9. I recommend installing it via uv. Something like:

uv tool install -p 3.14 pre-commit

Alternatively now that the Firefox build system doesn't depend on Taskgraph anymore.. we could also consider dropping 3.9 support in Taskgraph