So GH is dropping [1][2] native x86-64 (intel) macOS runners for FOSS by getting rid of the macos-13 VM. The CPython's CI is using it for builds in forks (and the upstream is relying on the Cirrus-provided image instead).

This is a tracking issue for figuring out how to best handle it before it starts causing disruption: brownouts will begin on Sep 1 (bringing flakiness into the CI runs in forks for the following 2.5 months), and the image will be gone completely on Nov 14.

Linked PRs

• gh-137638: Remove macos-13 from GitHub Actions #137989
• [3.13] gh-137638: Remove macos-13 from GitHub Actions #138000
• [3.12] gh-137638: Remove macos-13 from GitHub Actions #138001
• [3.11] gh-137638: Remove macos-13 from GitHub Actions #138002