Ignore linkcheck 403s from docutils.sourceforge.io

[woodruffw]

SourceForge appears to be sending HTTP 403s to the linkchecker, despite the links working just fine in a browser.

Unblocks #1996.

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📚 Documentation preview 📚: https://python-packaging-user-guide--1997.org.readthedocs.build/en/1997/

[woodruffw]

I can't reproduce this warning (which we treat as a hard error) locally:

/home/runner/work/packaging.python.org/packaging.python.org/source/tutorials/installing-packages.rst:376: WARNING: undefined label: 'pip:install_--no-binary'

The failing label definitely exists: https://pip.pypa.io/en/latest/cli/pip_install/#install-no-binary

Edit: now it reproduces, but I can't think of a reason this would suddenly fail. Sigh.

[woodruffw]

Oh hmm, this is because pip's RTD is pointing to latest instead of stable, and latest (which is for a development release) doesn't have --no-binary labeled seemingly.

Compare stable where it's documented at that anchor:

• https://pip.pypa.io/en/stable/cli/pip_install/#install-no-binary

And release where it isn't:

• https://pip.pypa.io/en/latest/cli/pip_install/#install-no-binary

So, I think there are two things here:

1. Should pip's default RTD site be stable, instead of latest? This would stop ReST ref churn between releases, which cause problems here. But I don't have a strong sense there.
2. I think that link to --no-binary was unintentionally removed, unless pip actually is fully removing --no-binary in the upcoming 26 release.

CC @ichard26 for opinions on the above 🙂

[woodruffw]

(One thing that's confusing me about this is that I can't find that --no-binary argument documentation anywhere on pip's main branch. It's not present in pip_install.rst and none of the recent changes look relevant.)

[notatallshaw]

@woodruffw this almost certainly due to this PR: pypa/pip#13769. Thanks for the catch, I will take a look before releasing.

[woodruffw]

Thanks a ton! I'm glad it served as a backstop here 🙂