Merged.

I took care of your comments and added a changelog entry. The only Python development dependency is tox now. It installs flake8 and pytest automatically in virtual environments. (I see now that there is no changelog entry for tox, issue930. I'll add one in the default branch.)

Adding Malte's comment as a change note:

I left a few small comments. Does this introduce new developer dependencies that we need to document? Perhaps not, because we already use pytest for other things?

Please add a changelog entry. Running tests is not so esoteric that we would hide this from the users.

Pull request: https://bitbucket.org/jendrikseipp/downward/pull-requests/143

We currently use a plain Python script to test that some standard configs successfully find a plan for a simple miconic task. Since we test a lot of configurations, the volume of output to stdout can become an annoyance, especially when trying to inspect it online for the Bitbucket Pipelines. Therefore, I'd like to use pytest to run the tests, which only shows stdout and stderr output for failing tests, making it easier to see where something went wrong.