Introduce %py3_check_import
With $PATH and $PYTHONPATH set to the %buildroot,
the macro tries to import the given Python 3 module(s).
Useful as a smoke test in %check when ruining tests is not feasible.
Accepts spaces or commas as separators.
Backport of https://src.fedoraproject.org/rpms/python-rpm-macros/c/c2305ea3