note that future_builtin's map is not quite like python 3's (closes #19363)
Patch by Gareth Rees.
diff --git a/Doc/library/future_builtins.rst b/Doc/library/future_builtins.rst
index 04f2052..62392eb 100644
--- a/Doc/library/future_builtins.rst
+++ b/Doc/library/future_builtins.rst
@@ -50,6 +50,11 @@
Works like :func:`itertools.imap`.
+ .. note::
+
+ In Python 3, :func:`map` does not accept ``None`` for the
+ function argument.
+
.. function:: oct(object)
Works like the built-in :func:`oct`, but instead of :meth:`__oct__` it will