That probably would have worked. I figured out what was going on, though I don't know why. Rather than pulling $releasever=6, it was pulling $releasever=$releasever. So I ran echo "6" > /etc/yum/vars/releasever and then ran your previous recommendation of updating app-base, and that worked. Then I removed the faked in variable and it still worked as it had updated the release rpm while updating app-base.