References: bnc#907958
Sanity check for those who forget '-X' on ssh and try to start virt-manager
Index: virt-manager-3.1.0/virtManager/virtmanager.py
===================================================================
--- virt-manager-3.1.0.orig/virtManager/virtmanager.py
+++ virt-manager-3.1.0/virtManager/virtmanager.py
@@ -62,8 +62,11 @@ def _import_gtk(leftovers):
             print("gtk3 3.22.0 or later is required.")
             sys.exit(1)
 
-        # This will error if Gtk wasn't correctly initialized
-        Gtk.init()
+        if 'DISPLAY' in os.environ and os.environ['DISPLAY']:
+            # This will error if Gtk wasn't correctly initialized
+            Gtk.Window()
+        else:
+            raise Exception("Error starting virt-manager: No graphical display found")
         globals()["Gtk"] = Gtk
 
         # This ensures we can init gsettings correctly