modulemd format is changing from v1 to v2. DNF supports modulemd via 'modulemd' package which won't get v2 support. DNF has to be ported to use libmodulemd: https://github.com/fedora-modularity/libmodulemd
We have to deploy new pungi which will generate modulemd v2 after the current Fedora infra freeze, which will be after 2018-03-27. We have no other opportunity to deploy this before another freeze before F28. It would be great to have support for this before this date, so we are not in situation when composes generates metadata which DNF cannot read.
There is PR for this: https://github.com/rpm-software-management/dnf/pull/1032
Yay, merged six days ago. When can we expect a release?
Fixed in dnf-2.7.5-9.fc28.
Oh, it issued against rawhide, in rawhide it is fixed in dnf-2.7.5-10.