bpo-23722: Raise a RuntimeError for absent __classcell__. (GH-6931)
A DeprecationWarning was emitted in Python 3.6-3.7.
diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst
index cc8dc95..855f241 100644
--- a/Doc/reference/datamodel.rst
+++ b/Doc/reference/datamodel.rst
@@ -1967,8 +1967,7 @@
as a ``__classcell__`` entry in the class namespace. If present, this must
be propagated up to the ``type.__new__`` call in order for the class to be
initialised correctly.
- Failing to do so will result in a :exc:`DeprecationWarning` in Python 3.6,
- and a :exc:`RuntimeError` in Python 3.8.
+ Failing to do so will result in a :exc:`RuntimeError` in Python 3.8.
When using the default metaclass :class:`type`, or any metaclass that ultimately
calls ``type.__new__``, the following additional customisation steps are