With all the bits in place we can now drop the 'setup.py' invocations
with preferred alternatives. The way to do this in a SPEC file is to
use either of the following macros: %tox or %pytest - both of which
automatically set paths for the test suite correctly which is
something we used to do ourselves in our implementation of the
setup.py's test command originally.
That is wrong and with the migration to PEP-517 compliant builds it
also won't work anymore properly, because there'd be no libs to import
by mangling PYTHONPATH, we'd only get an sdist or a wheel, or in case
of rpmbuild a preset buildroot environment.

Signed-off-by: Erik Skultety <eskultet@redhat.com>