Main purpose is we were using mySQL for config storage and we had some automation cases to modify the config on Non-NFV platforms. We have recently moved to NFV platforms. Hence planning to adapt automated cases to NFV environment.
For testing you can also use north interfaces like NETCONF or CLI. For this you do not need ConfD Python API, but you can still use Python test framework (like pytest). Good combination is pytest, pexpect (CLI) and ncc client (NETCONF) - all Python.