Description of problem: Customer requested this, basically they want a way to say "tell me what problems our current kickstart package selection will cause when we move from EL.N to EL.N+1. The have normal yum repos. of all the packages, they just want a repodiff to say things like "blah has been removed" (but only when blah is installed). I think this is just feeding the repodiff results through a package match.
yum and related packages are no longer actively developed. They are being replaced with dnf, dnf-utils, etc. I'm closing this bug because it's most likely never going to be fixed. If you still consider your bug report important, reopen it, please.