gh-127794: Validate header name according to rfc-5322

[srinivasreddy]

• Issue: email.message.EmailMessage accepts invalid header field names without error, which raise an error when parsed #127794

[bedevere-app]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

And if you don't make the requested changes, you will be put in the comfy chair!

[bitdancer]

Thanks for the prompt response. Hopefully I can be reasonably prompt in return, but unfortunately no guarantees :(

Requested changes were addressed

[picnixz]

Some final thoughts. Otherwise, it looks fine to me.

[picnixz]

I forgot to post my review 3 days ago..

[picnixz]

Great. The suggestion I proposed was meant to be checked with the online docs but RTD is currently failing for all other PRs. Have you tried rendering :rfc:`5322#section-3.6.8`? If this renders better (and I think we use this elsewhere), then I would recommend it above the title + ref form that we currently have.

Can you check it locally & show me a screenshot comparing the two? Thanks in advance.

[picnixz]

Nevermind, we use the long form anyway. No need to change:

$ git grep -P ':rfc:`.+ <\d{4}#section.+>' Doc/
Doc/howto/logging-cookbook.rst::rfc:`relevant section of the specification <5424#section-6>`.)
Doc/library/codecs.rst:based on the separator characters defined in :rfc:`section 3.1 of RFC 3490 <3490#section-3.1>`
Doc/library/http.client.rst:   an absolute path to conform with :rfc:`RFC 2616 §5.1.2 <2616#section-5.1.2>`
Doc/library/http.client.rst:   with the request. A :rfc:`Host header <2616#section-14.23>`
Doc/library/http.client.rst:   must be provided to conform with :rfc:`RFC 2616 §5.1.2 <2616#section-5.1.2>`
Doc/library/uuid.rst:   :rfc:`RFC 9562, §5.8 <9562#section-5.8>`.
Doc/library/xmlrpc.client.rst:      :rfc:`RFC 2045 section 6.8 <2045#section-6.8

[picnixz]

Once RTD is back online, we can merge this one I think.

[srinivasreddy]

@picnixz RTD passed as well. We can merge 🚀 🚀