argument providing a comparison function. Use the *key* argument
instead. N.B. the *key* and *reverse* arguments are now "keyword-only".
+* The :meth:`__cmp__` special method is no longer supported. Use :meth:`__lt__`
+ for sorting, :meth:`__eq__` with :meth:`__hash__`, and other rich comparisons
+ as needed.
+
* ``1/2`` returns a float. Use ``1//2`` to get the truncating behavior.
.. XXX move the next one to a later point, it's not a common stumbling block.