Updated `tuning.py` so it works with Python >=3.2

[DavidGoedicke]

Same issue as occurred in this other Github repo

Essentially, Python3.9 removed the function tostring() and we now need to use tobytes().

The change also includes a check for the minor version to run the new tobytes() function if we run in 3.2 or higher.

I hope this helps a little and addresses at least this one forum post.

[JamesOsborn-SE]

works on my machine

[vijay-prema]

LGTM. Approved.

[dynamicdavidrobert]

thank you a lot