bpo-36743: __get__ is sometimes called without the owner argument (#12992)

diff --git a/Tools/demo/eiffel.py b/Tools/demo/eiffel.py
index 736abea..a76c232 100755
--- a/Tools/demo/eiffel.py
+++ b/Tools/demo/eiffel.py
@@ -78,7 +78,7 @@
         self.__name__ = func.__name__
         self.__doc__ = func.__doc__
 
-    def __get__(self, obj, cls):
+    def __get__(self, obj, cls=None):
         return EiffelMethodWrapper(obj, self)
 
     def callmethod(self, inst, args, kwargs):