Package import errors when doing pip install -e

[ketch]

On a couple of Macs recently I've encountered the problem that the editable install command (pip install -e .) leads to setuptools failing to import packages that are installed (and yes, I've checked that they're installed for the correct Python installation on the machine). I get something like this:

I finally found a workaround in a comment here:

https://stackoverflow.com/questions/74876384/setuptools-doesnt-find-a-package-that-is-installed

Specifically, this command line works:

pip3 install --no-use-pep517 -e .

I don't yet know why; I guess that it has something to do with https://peps.python.org/pep-0517/

I'm posting this here in case others face the same problem, or in case somebody knows what the real issue is.