Thanks, however it turns out that this will unfortunately not work for
me: from astropys POV, pytest seems to be broken in versions 3.7 - 3.10;
according to linked issue, that bug is fixed in 3.10.1, which is in Debian unstable now.
I also observed diverse failures on other (astropy dependent) packages
with 3.10. Which basically means that I need to switch off the tests,
unless pytests upstream provides a bugfixed 3.X version.
maybe just disable some of that tests? Not whole testsuite?