On a Fedora 24 system, with gnome-software-3.20.3-1.fc24.x86_64 https://blogs.gnome.org/hughsie/2016/04/20/upgrading-fedora-23-to-24-using-gnome-software/ doesn't work to upgrade from f24 to f25 Sep 12 11:17:41 classic pk-offline-update[753]: failed to upgrade system: package kernel-4.8.0-0.rc4.git0.1.fc25.x86_64 cannot be verified and repo fedora is GPG enabled: failed to lookup digest in keyring for /var/cache/PackageKit/25/metadata/fedora/packages/kernel-4.8.0-0.rc4.git0.1.fc25.x86_64.rpm warning: /var/cache/PackageKit/25/metadata/fedora/packages/kernel-4.8.0-0.rc4.git0.1.fc25.x86_64.rpm: Header V3 RSA/SHA256 Signature, key ID fdb19c98: NOKEY
This should be already fixed with https://bodhi.fedoraproject.org/updates/FEDORA-2016-6bdfc07fa9