Another way is to use
Package: xserver-xorg-core Conflicts: xserver-xorg-video-6
(but that is a rather strong statement, though it will help the resolver to deal with the situation).
Another way is to use
Package: xserver-xorg-core xorg-video- 6
Conflicts: xserver-
(but that is a rather strong statement, though it will help the resolver to deal with the situation).