Error connecting: `ValueError: "port" must be None or a string, not <type 'list'>`

[cfobel]

Set up

1. Connect DropBot DX USB cable to computer.
2. Try to connect to DropBot DX:

import dropbot_dx as dx
proxy = dx.SerialProxy()

Expected behaviour

Successful connection to DropBot DX.

Observed behaviour

Error connecting: ValueError: "port" must be None or a string, not <type 'list'>

Cause

As of v1.2 (ec7016b), the dropbot_dx.SerialProxy class
explicitly specifies a list of COM ports to attempt to connect to.
However, support for specifying a list of ports to attempt to connect to was not added until base-node-rpc==0.19.