We serialise the tracker when storing it in redis (see rasa/tracker_store.py at master · RasaHQ/rasa · GitHub). Thus, you need to deserialise it on retrieval.
You can use the following code snippet:
#-- coding: utf-8 --
import redis
import json
import pickle
r = redis.Redis(host="localhost", port=6379, db=0)
json_test_dict = r.get("default")
dialogue = pickle.loads(json_test_dict)
print(dialogue)
The dialogue is of type Dialogue (rasa/conversation.py at master · RasaHQ/rasa · GitHub). It has a name and a list of events. Hope that helps.