It looks like Cython is failing to compile on docker. The version of Cython from the latest nightly run CI with nogil is the same as the one failing in this PR's docker image.

It could be that the docker image is out of date? According to docker hub, it was built one month ago, while there are commits in the nogil repo from 9 days ago.

Yep I naively thought the docker image was updated on each commit but I saw that it was not the case afterwards.

Not sure what the error is about, I can not reproduce locally so there may be some quirks with the CI environment ... I put this back in draft mode, this may not be worth the effort debugging it to be perfectly honest.

Interestingly the cython error disappeared on rerunning the CI ... I am going to close this since I have now included python nogil in #22448 and using the git clone is preferable to using a docker image that is updated every month.