Added changelog for JsonBase changes
Changes
=======
+x.xx.x (xxxx-xx-xx)
+-------------------
+- Fixes an issue causing a ``UnboundLocalError`` if an incoming
+ message to a service that had specified the enveloping
+ implementation ``JsonBase`` where JSON encoded but actually
+ wasn't originating from a source using a ``JsonBase`` compatible
+ envelope.
+
+
0.21.2 (2021-02-16)
-------------------
- Bugfix for an issue which caused the ``sqs.DeleteMessage`` API call
