gh-123430: Add dark mode support to pages generated by http.server

[YorikHansen]

The error pages and the directory lists generated by http.server did not allow browsers to enable the inbuilt dark mode. This change allows for that by setting the css property color-scheme properly.

• Issue: Add :root { color-scheme: light dark; } to http.server directory list and error pages #123430

[ghost]

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[bedevere-app]

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[hugovk]

main

Testing ./python.exe -m http.server and looking at a directory listing and an error page:

It's the same in light and dark mode on Chrome with macOS.

PR

In dark mode:

And in light mode it's the same as main.

[vstinner]

I cannot review the CSS, but I like @hugovk's screenshots and the feature.

[ZeroIntensity]

Should this get backported? The user seeing the incorrect color scheme sounds like a bug to me.

[vstinner]

Should this get backported? The user seeing the incorrect color scheme sounds like a bug to me.

It's a new feature, it should not be backported.

[hugovk]

@YorikHansen Please could you also mention this in What's New?

https://docs.python.org/3.14/whatsnew/3.14.html#improved-modules

[hugovk]

Thank you!