When unsubscribing _all_ topics, pubsub will drain the subscription channel to avoid deadlocks. See https://github.com/whyrusleeping/pubsub/pull/1. fixes #7803
When unsubscribing _all_ topics, pubsub will drain the subscription channel to avoid deadlocks. See https://github.com/whyrusleeping/pubsub/pull/1. fixes #7803