Issue #10734: Temporarily disable test_ttk test_heading_callback on 2.7 as well.

Lib/lib-tk/test/test_ttk/test_widgets.py

@@ -937,7 +937,8 @@ class TreeviewTest(unittest.TestCase):
         self.assertRaises(Tkinter.TclError, self.tv.heading, '#0',
             anchor=1)
 
-
+    # XXX skipping for now; should be fixed to work with newer ttk
+    @unittest.skip("skipping pending resolution of Issue #10734")
     def test_heading_callback(self):
         def simulate_heading_click(x, y):
             support.simulate_mouse_click(self.tv, x, y)