The only dependency mentioned by the yarl documentation is multidict and installing that makes no difference.  I see I can tell yarl to build a pure-python version to avoid compiling stuff.  If I do that it installs.  But what I actually wanted to do is install aiohttp, and that step fails with the exact same error message.

Given that it works in 3.10 but fails in 3.11a4, it does seem there is something about the new code that is involved here.