[pygobject] Gtk.DialogFlags.NO_SEPARATOR has been removed in Gtk 3.0

[John Palmieri <johnp src gnome org>]

commit 246877074617b0e9c3b2ba2a5395a73e0ed9cd5d
Author: John (J5) Palmieri <johnp redhat com>
Date:   Wed Sep 8 13:08:07 2010 -0400

    Gtk.DialogFlags.NO_SEPARATOR has been removed in Gtk 3.0

 gi/overrides/Gtk.py |   10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)
---
diff --git a/gi/overrides/Gtk.py b/gi/overrides/Gtk.py
index 8a7cb6a..fc7b28c 100644
--- a/gi/overrides/Gtk.py
+++ b/gi/overrides/Gtk.py
@@ -256,8 +256,14 @@ class Dialog(Gtk.Dialog):
             self.set_modal(True)
         if flags & Gtk.DialogFlags.DESTROY_WITH_PARENT:
             self.set_destroy_with_parent(True)
-        if flags & Gtk.DialogFlags.NO_SEPARATOR:
-            self.set_has_separator(False)
+
+        # NO_SEPARATOR has been removed from Gtk 3
+        try:
+            if flags & Gtk.DialogFlags.NO_SEPARATOR:
+                self.set_has_separator(False)
+        except AttributeError:
+            pass
+
         if buttons:
             self.add_buttons(*buttons)