dev-python/libvirt-python should be stable enough that a negative version constraint "<" should not be necessary. For example, the package did not change at all between 1.2.21 and 1.3.0 and had very little modifications before that for quite a while. The big problem with above constraint is that it interferes with upstream's frequent monthly releases and our (usually monthly) stabilization of a new version and immediate removal of the older one.
updated dep to <=1.3.0 as per the current stable branches requirements files (but not the tag, this is a compromise).
