The python3-netaddr (0.7.19-6.fc28) RPM requires both Python 2 and Python 3:
$ dnf --disablerepo=* --enablerepo=rawhide repoquery --requires python3-netaddr | grep python
python(abi) = 3.6
This happened due to recently introduced shebangs mangling , and you might see the warnings in the build log:
> + /usr/lib/rpm/redhat/brp-mangle-shebangs
> *** WARNING: mangling shebang in ./usr/bin/netaddr3 from #!/usr/bin/env python -s to #!/usr/bin/python2 -s. This will become an ERROR, fix it manually!
The executable contains `#!/usr/bin/env python` shebang, which is forbidden by the guidelines and is automatically mangled to `#!/usr/bin/python2` during build. Please fix the shebang to be `#!/usr/bin/python3` explicitly  or remove the executable bit from the above file if not needed.
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!