Issue #27312: mock out function that fails when called from setupApp during
IDLE test_macosx and see if addOpenEventSupport() fails.
diff --git a/Lib/idlelib/idle_test/test_macosx.py b/Lib/idlelib/idle_test/test_macosx.py
index d7f8f5d..189dc48 100644
--- a/Lib/idlelib/idle_test/test_macosx.py
+++ b/Lib/idlelib/idle_test/test_macosx.py
@@ -83,6 +83,7 @@
         cls.root.destroy()
         del cls.root
 
+    @mock.patch('idlelib.macosx.overrideRootMenu')  #27312
     def test_setupapp(self):
         "Call setupApp with each possible graphics type."
         root = self.root