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
/usr/bin/python2
python(abi) = 3.6
...

This happened due to recently introduced shebangs mangling [0], 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 [1] 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!

[0] https://pagure.io/packaging-committee/issue/738#comment-490366
[1] http://python-rpm-porting.readthedocs.io/en/latest/application-modules.html#fixing-shebangs