Deadlock when executing mqtt-tests

[felixbohnus]

If you run

pytest .\dir\

the tests sometimes stops without any further progress.
After a short investigation it seems like tavern runs into a deadlock.
The problem seems to be that the paho-client uses another thread for executing the callbacks.

As a result the subscribe_lock of the client.py creates a deadlock

[michaelboulton]

I've made a minor modification to the locks in #850 but I can't see anything else that could cause a deadlock. A related question, which version of paho-mqtt are you using? I know some people were having issues with the most recent version, you could try using version 1.5.0 or 1.5.1 and see if that works

[michaelboulton]

This should be fixed in 2.0.5, if not then I suspect it's an issue in paho-mqtt