[pygobject] Don't issue a depreciation warning for GtkDialog's NO_SEPARATOR flag, even when unused

[Sebastian Polsterl <sebp src gnome org>]

commit d6a899cdf70e978534326155e3fad75a705f4b20
Author: Sebastian PÃlsterl <sebp k-d-w org>
Date:   Sat Feb 4 15:55:55 2012 +0100

    Don't issue a depreciation warning for GtkDialog's NO_SEPARATOR flag, even when unused
    
    https://bugzilla.gnome.org/show_bug.cgi?id=665553

 gi/overrides/Gtk.py |    6 ++----
 1 files changed, 2 insertions(+), 4 deletions(-)
---
diff --git a/gi/overrides/Gtk.py b/gi/overrides/Gtk.py
index 3b3055c..e24a2de 100644
--- a/gi/overrides/Gtk.py
+++ b/gi/overrides/Gtk.py
@@ -411,10 +411,8 @@ class Dialog(Gtk.Dialog, Container):
             self.set_destroy_with_parent(True)
 
         # NO_SEPARATOR has been removed from Gtk 3
-        try:
-            if flags & Gtk.DialogFlags.NO_SEPARATOR:
-                self.set_has_separator(False)
-        except AttributeError:
+        if hasattr(Gtk.DialogFlags, "NO_SEPARATOR") and (flags & Gtk.DialogFlags.NO_SEPARATOR):
+            self.set_has_separator(False)
             import warnings
             warnings.warn("Gtk.DialogFlags.NO_SEPARATOR has been depricated since Gtk+-3.0", DeprecationWarning)