rpm: add dbus-python dependency

This package is required by lots of stuff in Fedora anyway, but this
doesn't mean that we can have broken dependencies.

rpm_spec/core-vm.spec

@@ -51,6 +51,7 @@ Requires:   qubes-utils
 Requires:   initscripts
 # for qubes-desktop-run
 Requires:   pygobject3-base
+Requires:   dbus-python
 # for qubes-session-autostart
 Requires:   pyxdg
 %if %{fedora} >= 20