[3.0] Support setuptools >= 61.2 in Python tests
Fix for #253 (closed), by mirroring the change from https://github.com/pypa/setuptools/pull/3258/commits/1c23f5e1e4b18b50081cbabb2dea22bf345f5894
This is the 3.0 version of !897 (merged), with the difference that the 3.0 branch already has python3-setuptools
in .gitlab-ci.yml
and therefore doesn't need the commit that updates .gitlab-ci.yml
.