I'm glad to see unittest module!  I think this one may benefit from skipping all tests if selinux is unknown to the system.  For example, I think SLES uses some "App armor" thing instead.  Since we cannot predict what kind of host/environment unittests will run, if selinux is unknown, then maybe all tests should skip or not run.  This is same reason I had to write <code>dummy_virsh</code> stuff, it's annoying, but we must deal with it.