Load payload using the JSONDecoder

The payload is dumped using the JSONEncoder so it should be loaded using the
proper decoder.

issue8024
review56551002

trytond/bus.py

@@ -21,7 +21,7 @@ from werkzeug.exceptions import NotImplemented, BadRequest
 from trytond import backend
 from trytond.wsgi import app
 from trytond.transaction import Transaction
-from trytond.protocols.jsonrpc import JSONEncoder
+from trytond.protocols.jsonrpc import JSONEncoder, JSONDecoder
 from trytond.config import config
 from trytond.tools import resolve
 
@@ -162,7 +162,9 @@ class LongPollingBus:
                 conn.poll()
                 while conn.notifies:
                     notification = conn.notifies.pop()
-                    payload = json.loads(notification.payload)
+                    payload = json.loads(
+                        notification.payload,
+                        object_hook=JSONDecoder())
                     channel = payload['channel']
                     message = payload['message']
                     messages.append(channel, message)