Readme is unclear about requirements
The Readme says:
Even if Mailman 3 runs on Python 3, the web interfaces and the commands in this procedure run on Python 2.7, so make sure your system Python version is 2.7.
What exacly does this mean? Does the front-end require Python 2.7? Or is is just this bundler package using Python 2.7 by chance or personal preference? Or is this setup-tool written in Python2?