Infra: Add nicer 404 page

[hugovk]

Right now if you typo a PEP (e.g. https://peps.python.org/pep-123456) you get the default GitHub Pages 404 page:

This is an attempt to use a nicer one using our own Sphinx theme:

I have this on my fork right now: https://hugovk.github.io/peps/pep-123456

The one difference is I have notfound_urls_prefix = "/peps/" in conf.py because it's using the github.io domain and a peps/ subdir. See:

https://sphinx-notfound-page.readthedocs.io/en/latest/faq.html#does-this-extension-work-with-github-pages

We'll probably need to merge this to see if it works properly.

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📚 Documentation preview 📚: https://pep-previews--4184.org.readthedocs.build/

[StanFromIreland]

docs.python.org needs one too but I'm unsure how to implement it. The package sphinx-notfound-page is broken so I guess we just create a simple html page that can be added to the nginx conf.

[hugovk]

docs.python.org needs one too but I'm unsure how to implement it. The package sphinx-notfound-page is broken so I guess we just create a simple html page that can be added to the nginx conf.

Let's continue that in python/cpython#125895

[AA-Turner]

I remember we initially had problems with a custom 404 page due to redirects to PEP 404, but this is now done proxy-side with the TF config, so hopefully there won't be problems now.

A

[hugovk]

There we go :)

https://peps.python.org/pep-123456