This will make sure that when running |mach python-test --python 3| locally, we only run the tests that also run in CI with python 3 (and therefore pass presumably). MozReview-Commit-ID: 3OBr9yLSlSq
==== mach ==== Mach (German for *do*) is a generic command dispatcher for the command line. To use mach, you install the mach core (a Python package), create an executable *driver* script (named whatever you want), and write mach commands. When the *driver* is executed, mach dispatches to the requested command handler automatically. To learn more, read the docs in ``docs/``.