Log Message:
py-octoprint: update to version 1.6.1

This is a bugfix release to fix two bugs in 1.6.0.

The full list of changes from version 1.5.3 to 1.6.0 can be found at
https://github.com/OctoPrint/OctoPrint/releases/tag/1.6.0.

This also improves the RC script provided to not longer assume Python 3.8
specifically.