GH-136155: Fail the EPUB check on fatal errors

[AA-Turner]

We also split epub to a parallel job.

A

• Issue: Docs: EPUB builds are broken #136155

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📚 Documentation preview 📚: https://cpython-previews--137351.org.readthedocs.build/

[hugovk]

We also split epub to a parallel job.

The original PR had these as parallel jobs, but I asked to keep them in the same one because they have a lot of duplicate setup config :)

#134074 (comment)

[AA-Turner]

True, though the setup for epub alone is far simpler & easier to comprehend. I think splitting is useful, without doing so the docs job takes ~2 minutes longer, which delays feedback if the PR is good to leave as-is. It's rare for doctest to fail & docs to pass.

A

[miss-islington-app]

Thanks @AA-Turner for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14.
🐍🍒⛏🤖

[miss-islington-app]

Sorry, @AA-Turner, I could not cleanly backport this to 3.14 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker b4a1974aa2af63c4754846af9abfb436372e19c7 3.14

[miss-islington-app]

Sorry, @AA-Turner, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker b4a1974aa2af63c4754846af9abfb436372e19c7 3.13

[AA-Turner]

I've cherry-picked this commit into #137538 & #137539.