make htmllive -> "Not Found"

[hugovk]

Describe the bug

On macOS:

make clean htmllive

It builds and serves the site:

...
The HTML pages are in _build/html.
[sphinx-autobuild] Serving on http://127.0.0.1:55301
[sphinx-autobuild] Waiting to detect changes...

But http://127.0.0.1:55301 shows "Not Found" in the browser.

Expected behavior

Devguide is shown instead of "Not Found".

I think this is caused by #1370, but sphinx-doc/sphinx-autobuild#175 makes it hard to test old commits.

With git checkout 9447a88d894b932916d220f0687e432c5bd81cd8 (the commit before #1370) and:

diff --git a/requirements.txt b/requirements.txt
-sphinx-autobuild
+sphinx-autobuild<2024.9

Then it serves the site as expected.

cc @AA-Turner