[jimminy]

Tox is designed for environment isolation, and primarily for testing against multiple release targets.

It's not an awful choice, when it's exactly what you want to do. The dependency is that tox will run the tests against a Python 3.6 target environment and a Python 3.8 target environment.

The dual requirement is asking for test assurance that Yamale will work with 3.6 or 3.8.