[iennae]

Description

Makes Python 3.12 the minimum for the shared nox setup, and stops lint from asking contributors for a Python 3.10 interpreter. 3.10 reached end of life in Oct 2026.

Problem: most samples only tested 3.10 and 3.14, and lint ran on each sample's oldest tested version (3.10). Contributors on 3.12 hit missing-interpreter errors for 3.10 and saw py-3.12 skipped.

Changes

• noxfile-template.py
  • ALL_VERSIONS is now 3.12–3.15; 3.8–3.11 are removed.
  • The default tests 3.12 + 3.14 (the minimum and the latest stable version).
  • LINTING_VERSION is fixed at 3.12.
  • New OPT_IN_VERSIONS = ["3.15"] and an "opt_in_versions" config key. Existing configs only list the versions they skip, so without this every one of them would start testing 3.15 at once.
• noxfile_config.py (root default): ignored_versions = ["3.13"], opt_in_versions = [], plus comments on how to opt in to 3.13 and 3.15.
• .github/workflows/lint.yml and .github/scripts/noxfile-lint.py: the lint job uses Python 3.12. Also fixes two flake8 issues and black formatting that were already in that file.

Leftover version strings in per-sample configs, such as "3.8", are now ignored.

Follow-ups (not in this PR)

• Per-sample noxfile_config.py files that copied the old default (ignore 3.8, 3.9, 3.11, 3.12, 3.13) now test only 3.14. A follow-up PR will update them to 3.12 + 3.14.
• Update the Kokoro testing image (.kokoro/docker, .trampolinerc) and remove the old .kokoro/python3.8–3.11 configs.

Verification (local nox 2026.10.20, CPython 3.12.16 / 3.14.10)

Scenario	Tested versions	Lint version
No local config (template default)	3.12, 3.14	3.12
Root noxfile_config.py	3.12, 3.14	3.12
Copied old config (e.g. alloydb/notebooks)	3.14	3.12
opt_in_versions: ["3.15"]	3.12, 3.14, 3.15	3.12

• nox -s lint on cloud_scheduler/ created its env with python3.12 and passed.
• The GitHub lint noxfile (flake8 + black) passes on the changed files.

Checklist

Testing

• I have tested this change on a live environment and verified it works as intended. (Tested locally with nox. These are CI and tooling changes, so there's no deployed sample to check.)

Compliance & Style

• I have followed the Sample Guidelines.
• The README is updated with all relevant information (if applicable). N/A
• If this PR adds a new sample directory: I updated the CODEOWNERS file. N/A

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Post-Approval Actions

• Please merge this PR for me once it is approved

[gemini-code-assist]

Code Review

This pull request updates the supported Python versions across the Nox configuration files, raising the minimum supported version to 3.12 and adding support for up to 3.15. It also introduces an opt-in mechanism for newly released Python versions and sets the linting version to 3.12. A review comment suggests improving the robustness of the version filtering logic in noxfile-template.py by using (TEST_CONFIG.get("opt_in_versions") or []) to prevent potential TypeError exceptions if the configuration explicitly overrides the key to None.

[gemini-code-assist]

To make the version filtering more robust and prevent potential TypeError exceptions, use TEST_CONFIG.get("opt_in_versions") or [] instead of TEST_CONFIG.get("opt_in_versions", []). If a user's custom noxfile_config.py explicitly overrides opt_in_versions to None or another falsy value, .get(..., []) would still return None, leading to a TypeError: argument of type 'NoneType' is not iterable during the membership check.

Suggested change

	and (v not in OPT_IN_VERSIONS or v in TEST_CONFIG.get("opt_in_versions", []))
	and (v not in OPT_IN_VERSIONS or v in (TEST_CONFIG.get("opt_in_versions") or []))

[XrossFox]

LGTM