Description of problem:
When I try to upgrade from F20 to F21 I get:
Error: Package: xorg-x11-drv-mga-1.6.2-8.fc20.x86_64 (@koji-override-0/$releasever)
           Requires: xserver-abi(videodrv-14) >= 1
           Removing: xorg-x11-server-Xorg-1.14.4-11.fc20.x86_64 (@updates/20)
               xserver-abi(videodrv-14) = 1
           Updated By: xorg-x11-server-Xorg-1.15.99.904-3.fc21.x86_64 (fedora)
              ~xserver-abi(videodrv-18) = 0

This is because xorg-x11-drv-mga has been installed by default in F20, but is not distributed any more in F21.
To provide clean update path you should put:
  Obsoletes: xorg-x11-drv-mga <= 1.6.3
in your spec file -- .3 because we need to be higher then %{versions} + dist tag.)


Version-Release number of selected component (if applicable):
xorg-x11-server-Xorg-1.15.99.904-3.fc21.x86_64

How reproducible:
always

Steps to Reproduce:
1. From F20: yum --releasever=21 distro-sync