Raise exception if cannot connect to push channel

.. because we need a working request session in order to set up
a working push session.

src/zinolib/controllers/zino1.py

@@ -284,7 +284,8 @@ def connect_push_channel(session):
         if session.request.connected and session.request.authenticated:
             session.push = notifier(session.request)
             session.push.connect()  # ntie
-        return session
+            return session
+        raise NotConnectedError("Not connected tp request channel, so cannot connect to push channel")
 
     @staticmethod
     def authenticate(session, username=None, password=None):