So, turns out I got this right somehow (setup.py defaults to distutils) but not really:
We don't even use setup.py but build the portmidi python module directly
(cython/gcc/install). I removed setup.py and rebuilt, this works fine and produces the
same package.
So, I suggest removing setup.py in spec and not installing the shipped README (which does
not match the installation). I'm not the owner/main admin/you name it, so I'll
suggest this to the portmidi team as a PR to have possible technical discussions there.