How to determine lowest version of Python 3 to run?

[Christopher Reimer]

Greetings,

I've always installed the latest and greatest version of Python 3 to develop my own programs. I'm planning to release a program to the public. I could toss in a note that the program runs on the latest version of Python 3.6 but I haven't tested on earlier versions (i.e., 3.4 and 3.5). AFAIK, I haven't written any version-specific code.

How do I determine the lowest version of Python to run?

I'm leaning towards installing the latest minor version of each available major version, running tox to run the unit tests against each one, and seeing what blows up.

Thank you, 

Chris R.