This was discovered in Pub/Sub, whereby futures dependent on this class hang if not set with a timeout when a throw occurs in BackgroundConsumer's _thread_main.

When we open a BackgroundConsumer, if something within the try block, e.g. open, throws, then the exception clauses log but do not close the underlying stream or thread.

I believe this will be fixed by adding self.stop() when exceptions are caught. This appears consistent with the intent of the class as per the docstring. Then, the bidi_rpc will call our add_done_callback to surface the error.

I will be submitting a PR to address this.