There are some packages (eg, yaboot) which only exist on some architectures.
yum doesn't check that the package actually exists before using it to key
whether or not a group is installed or not.
We're going to need to provide to comps.compile() a list of all the available
package tuples so it can see if it is there, or not.
That's a lot of crap it suddenly needs to know about.
Worked around just by changing the (small number) of packages in question.