For modulemd-resolver we need at least the python2 version installed:

{{{
% yum ls python?-solv
Loaded plugins: aliases, copr, langpacks, verify
Installed Packages
python2-solv.x86_64 0.6.20-2.fc23 @updates
Available Packages
python3-solv.x86_64 0.6.20-2.fc23 updates
}}}

...if there's no harm in the python3 one, then might as well put that in too.