In case of reconnection to MQTT broker subscriptions are lost

[JohannesHennecke]

Describe the bug
When connection to the MQTT broker is lost for a short time, mqtt-io reconnects to the broker and is able to publish again. But the subscriptions to topics which were made when mqtt-io first connected to the broker, are lost. That means, that after the reconnection mqtt-io does not react anymore when requests are made using those topics.

Expected behavior
The subscriptions should be repeated directly after the reconnection.

Error messages and traceback

Paste any error messages and Python traceback if applicable.

Config

Hardware
Raspberry Pi 4

• Connected hardware: custom testboard

System:

• OS: Raspbian
• Python version: 3.7.3
• User you're running as: pi
• Using a virtualenv?: no

Additional context
I have implemented a solution for this problem and would like to commit it.