Tests for @abstractproperty by Jeffrey Yasskin.
(The previous changes to abc.py were also by him).
Put back a comment about using super() for properties
(I didn't realize this worked).
diff --git a/Lib/abc.py b/Lib/abc.py
index ab6325e..07836e6 100644
--- a/Lib/abc.py
+++ b/Lib/abc.py
@@ -30,6 +30,8 @@
     Requires that the metaclass is ABCMeta or derived from it.  A
     class that has a metaclass derived from ABCMeta cannot be
     instantiated unless all of its abstract properties are overridden.
+    The abstract properties can be called using any of the the normal
+    'super' call mechanisms.
 
     Usage: