I ran into this on one of my Pi's last week. It turned out to be that we use a package called paho-mqtt, and we're expecting version 1.2.3 with the example code with have in Github. When version 1.3.0 is installed, it left that error message. While we need to adjust our code so it will play nice with 1.3.0, in the meantime this can be worked around by simply installing v1.2.3 of the paho-mqtt package.
You can first check to make sure that it is the same thing, if you have paho-mqtt 1.3.0 running:
pip show paho-mqtt
Assuming you are, to change it to version 1.2.3:
sudo pip install paho-mqtt==1.2.3
Again you could run
pip show paho-mqtt to verify the change was made correctly. At this point you should be able to run our example code without that error message about the number of arguments.