validate <variant id=X> values actually exist
and elements can have an optional value inside, referencing a top level value. But I don't think anything actually validates that the references are correct. osinfo_media_get_os_variants will do it in a round about way, but it should probably be a warning condition in the loader, like when upgrades/derives/etc relation isn't correct. Or maybe just an osinfo-db test case
Edited by Cole Robinson