[meld] undo: Use py3k-style super

[Kai Willadsen <kaiw src gnome org>]

commit 120b945f384e58668228d29a98c22770dd285cb9
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Sun Feb 11 08:43:24 2018 +1000

    undo: Use py3k-style super

 meld/undo.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/meld/undo.py b/meld/undo.py
index 7f224938..3c1695ba 100644
--- a/meld/undo.py
+++ b/meld/undo.py
@@ -84,7 +84,7 @@ class UndoSequence(GObject.GObject):
         expects to maintain undo checkpoints for the same set of
         buffers for the lifetime of the UndoSequence.
         """
-        GObject.GObject.__init__(self)
+        super().__init__()
         self.buffer_refs = [weakref.ref(buf) for buf in buffers]
         self.clear()