The python2-mathgl (2.4.1-6.fc29) RPM requires both Python 2 and Python 3:
$ dnf --repo=rawhide repoquery --requires python2-mathgl | grep python
python(abi) = 2.7
python(abi) = 3.7
Except in very special circumstances, there is no need for one package
to drag in both Python stacks. Usually, this is a packaging error: for
example, a stray "/usr/bin/python" shebang in a Python 3 package can
introduce a Python 2 dependency.
Please split your package, or remove the stray dependencies.
There is a section on shebangs in the Python RPM Porting Guide 
which covers this issue.
It's ok to do this in Rawhide only, however, it would be greatly
appreciated if you could push it to Fedora 28 as well.
If anything is unclear, or if you need any kind of assistance, you can
ask on IRC (#fedora-python on Freenode), or reply here. We'll be happy
to help investigating or fixing this issue!
This bug appears to have been reported against 'rawhide' during the Fedora 29 development cycle.
Changing version to '29'.
This bug appears to have been reported against 'rawhide' during the Fedora 30 development cycle.
Changing version to '30'.
This is fixed, at least on Rawhide and f30.