FIX: backward compat for types.ClassType attribute (#359)

* FIX: backward compat for types.ClassType attribute

* typo

* Add entry to changelog

Author: ogrisel

Diff for: CHANGES.md

@@ -1,6 +1,9 @@
 1.4.1 (in development)
 ======================
 
+- Restore compat with loading dynamic classes pickled with cloudpickle
+  version 1.2.1 that would reference the `types.ClassType` attribute.
+  ([PR #359](https://github.com/cloudpipe/cloudpickle/pull/359))
 
 
 1.4.0

Diff for: cloudpickle/cloudpickle.py

@@ -388,6 +388,11 @@ def _cell_set_factory(value):
 
 
 def _builtin_type(name):
+    if name == "ClassType":  # pragma: no cover
+        # Backward compat to load pickle files generated with cloudpickle
+        # < 1.3 even if loading pickle files from older versions is not
+        # officially supported.
+        return type
     return getattr(types, name)