With 1.4.2 the code no longer checks for xenpv when adding
a usb tablet which is only supported on xen hvm.

Index: virt-manager-1.4.3/virtinst/guest.py
===================================================================
--- virt-manager-1.4.3.orig/virtinst/guest.py
+++ virt-manager-1.4.3/virtinst/guest.py
@@ -660,7 +660,7 @@ class Guest(XMLBuilder):
 
         usb_tablet = False
         usb_keyboard = False
-        if self.os.is_x86():
+        if self.os.is_x86() and not self.os.is_xenpv():
             usb_tablet = self._os_object.supports_usbtablet()
         if self.os.is_arm_machvirt():
             usb_tablet = True