tests.yml and release.yml: the Python 3.9 jobs run on ubuntu-latest, which now gives out Ubuntu 26.04 runners with no 3.9 for setup-python, so package fails there and the release's 3.9 install check would too #1094

Found by lane 3 on #1092's CI run of 2026-10-21T04:35Z.

What happens. ubuntu-latest has started giving out Ubuntu 26.04 runners, and setup-python has no Python 3.9 build for Ubuntu 26.04.

• The package job of tests.yml (runs-on: ubuntu-latest, python-version: '3.9', :242-251) failed in its setup-python step at 04:35:25Z: The version '3.9' with architecture 'x64' was not found for Ubuntu 26.04. Its job is https://github.com/opensoft/openRepoShape/actions/runs/39544729996/job/119040615170.
• actions/python-versions' versions-manifest.json (read 04:39Z) lists x64 builds for Ubuntu 26.04 of 3.10 to 3.15 only. For 24.04 it lists 3.8 to 3.15.
• package passed on main's push run at 01:27Z and on the family root's bootstrap.py: credential_advice and ended_on say a member's failed clone ends git's update with 1 before any checkout but a leg's lets it go on, and killed_said says git's update was itself killed, not that it went on (#1085) #1088, shape_materialize.py, adopt-project.py and bump-leg.py: a tag a clone holds without its commit is one it cannot answer for, check says a commit it cannot ask was not asked, and a pinned product YAML 1.1 or 1.2 reads as no text is quoted (#912) #1090 and adopt-project.py: check names what the clone's .git holds as git keeps refs, and asks a pin's file through the links the root keeps, so a link into .git or onto a pin's file is refused before any leg or adopted with the copy beside it (#904) #1091, so the image is rolling out and a run fails when it lands on a new runner.

Why it matters.

• Pilots. Every landing pilot checks main's newest push run. Once a package job on main lands on a 26.04 runner, that run is red, and every lane's pilot stops until main is green again. This holds even though package is not among the checks a pilot waits for on a PR (tests and SonarCloud).
• The release. The release's install check has a row {os: ubuntu-latest, python: '3.9'} (release.yml:874-875, "the oldest Python the package supports"), so the v1.2.0 release would fail there too.

Fix.

• Run the two 3.9 jobs on ubuntu-24.04, which has 3.9 builds, with a comment saying why. The other jobs ask for 3.x or 3.12, which 26.04 has, so they stay on ubuntu-latest.
• Update tests/test_release_workflow.py:562-564, which pins the install matrix's runners.
• requires-python stays >=3.9. Dropping 3.9, which has been past its end of life since October 2025, is Brett Heap's call and not this fix's.

Lane: openreposhape-3 (openRepoShape-3)