Building python PyPI package in copr

edit

I want to use copr to package some python packages for Fedora, which are currently not in the official repos, but in PyPI. When I choose PyPI as source, no package I tried was built successfully and it showed no error obvious to me in the logs. In the end the build is still marked as failed.

So my question is how to get the build running properly. Are there any prerequisites I have to respect for a package with PyPI as source to build successfully?