package-changer stuck, "MethodCallError: Session ID must be set before attempting to send a message"

[Andreas Hasenack]

I don't know what is going on, but the package related activities for our test ls3-precise machine are stuck "in progress", and that client has this message over and over in the package-changer.log file:

2013-07-09 18:39:45,339 INFO [MainThread] Queuing response with change package results to exchange urgently.
2013-07-09 18:39:45,341 ERROR [MainThread] None
MethodCallError: Session ID must be set before attempting to send a message

I tried identifying where this was happening, but the code seems to like to swallow tracebacks and won't tell me where the call came from. All I know is that it reached this bit in broker/server.py:
"""
    @remote
    def send_message(self, message, session_id, urgent=False):
(...)
        if session_id is None:
            raise RuntimeError(
                "Session ID must be set before attempting to send a message")
"""