chore(versions): update Python version support to 3.10+ in gapic-generator

[chalmerlowe]

Note

This PR has been updated to remove 3.7, 3.8, and 3.9 (with one exception discussed below).

Overview

This Pull Request updates the gapic-generator package and related CI configurations to reflect the deprecation of Python 3.7 through 3.9. It updates documentation, templates, and CI scripts to establish Python 3.10 as the new minimum supported version where applicable.

Changes

Documentation:

• Updated installation and verification instructions in packages/gapic-generator/docs to reference Python 3.10

Templates:

• Updated init.py.j2 templates in gapic/ads-templates to require Python 3.10+ (updating sys.version_info checks and error messages).
• Removed outdated comments regarding Python 3.9 and below features (like module-level getattr) to avoid confusion, as the baseline runtime is now higher than the version noted in the comments.
• Updated mypy.ini.j2 to target Python 3.10.
• Cleaned up dead code (e.g. commented-out Jinja snippets) in the templates.

CI Configurations:

• Removed Python 3.9 and below from the unit test matrix in ci/run_single_test.sh.
• Updated comments regarding supported Python versions in ci/run_conditional_tests.sh.

Reasoning

Python 3.9 and below have reached End-of-Life (EOL) and are no longer supported. These changes ensure that our generator and the libraries it produces align with current support policies and reduce maintenance burden by removing dead code paths.

Note

because the config that runs this PR checks is not updated yet, it still wants to run 3.9 so we have a temp change to skip that nox session. Once this PR merges future PRs will no longer attempt to run 3.9 and we will follow-up with a small PR to strip out that last 3.9 reference.

Fixes internal issue: http://b/482126936 🦕

[gemini-code-assist]

Code Review

This pull request removes support for Python 3.7 across the repository, updating documentation, CI scripts, and generator templates to reflect a minimum requirement of Python 3.8. Feedback was provided to ensure consistency between CI scripts by including Python 3.13 in the list of supported versions within the comments of ci/run_conditional_tests.sh.