Ohhh, interesting, cgitb depends on pydoc, so if I use css in pydoc... oh wow.

So I modified cgitb a bit to not depend on html rendered by pydoc.

I also had to modify pydoc test which were extremely strict in the output expected, I tried to still check that every bit of important info are given, while not being strict on the HTML used.

TIL about ServerHTMLDoc...

I'd like to merge this, does someone still want to proof-read first?

I haven’t had a chance to run it locally to see the results yet.
Maybe you have screenshots?

This could get a note in the release notes (for pydoc and xmlrpc — cgitb is unchanged)

Here come the screenshots, side by side:

There's a few differences, in the height of the title bar for example.

This could get a note in the release notes (for pydoc and xmlrpc — cgitb is unchanged)

True, done.

Thank you for your efforts in tackling this! It was needed and is the basis for future improvements.

I have added some final questions on some details. (If you make changes, please avoid force-pushing to make reviewing easier.)

Thanks @merwok and @rhettinger for the review!