Tests fail on master after latest merge

[HerrMuellerluedenscheid]

Hi @shipmints,
I ran a git bisect on master as some tests failed and some were hanging forever (python 3.7.1). I found that commit 1f5efd383f85657a64eaca6ce37aecb360788293 introduced some errors.
Can you run the tests on your end and check if the tests pass?
Regards
Marius

[HerrMuellerluedenscheid]

Specifically

test_client_publish_retain_subscribe (tests.test_broker.BrokerTest) ... FAIL
test_client_subscribe (tests.test_broker.BrokerTest) ... ERROR
test_client_subscribe_invalid (tests.test_broker.BrokerTest) ... ERROR
test_client_subscribe_publish (tests.test_broker.BrokerTest) ... ERROR
test_client_subscribe_publish_dollar_topic_1 (tests.test_broker.BrokerTest) ... ERROR
test_client_subscribe_publish_dollar_topic_2 (tests.test_broker.BrokerTest) ... ERROR
test_client_subscribe_twice (tests.test_broker.BrokerTest) ... ERROR
test_client_unsubscribe (tests.test_broker.BrokerTest) ... ERROR
test_start_stop (tests.test_broker.BrokerTest) ... ERROR

Please note #230 Thus, you may have to download the latest certificate from http://test.mosquitto.org/ssl/mosquitto.org.crt

[HerrMuellerluedenscheid]

The failure above is discussed in this comment 1f5efd3#r45823488
@njouanin do you have an opinion?

[HerrMuellerluedenscheid]

I reverted 1f5efd3. Turned out that the errors follow from the broken test test_client_publish_retain_subscribe