Pymodbus integration is outdated/broken

[D-VR]

While trying to get the modbus part of example s3-2017 running, I've noticed that minicps is written against pymodbus version 1.3.2, which is very out of date (current pymodbus uses a different structure / api). In addition, installing pymodbus==1.3.2 doesn't work for any python versions above 3.6 as it's using the reserved keyword async.