This commit:
1. Formats all of our existing code using `black`.
2. Adds a note about using `black` to `CONTRIBUTING.rst`.
3. Runs `black --check` as part of CI (failing builds that aren't properly formatted).
Previously, we were running the test suite for several combinations of MongoDB,
Python, and PyMongo:
- PyPy, MongoDB v2.6, PyMongo v3.x (which really means v3.6.1 at the moment)
- Python v2.7, MongoDB v2.6, PyMongo v3.x
- Python v3.5, MongoDB v2.6, PyMongo v3.x
- Python v3.6, MongoDB v2.6, PyMongo v3.x
- Python v2.7, MongoDB v3.0, PyMongo v3.5.0
- Python v3.6, MongoDB v3.0, PyMongo v3.5.0
- Python v3.5, MongoDB v3.2, PyMongo v3.x
- Python v3.6, MongoDB v3.2, PyMongo v3.x
- Python v3.6, MongoDB v3.4, PyMongo v3.x
- Python v3.6, MongoDB v3.6, PyMongo v3.x
There were a couple issues with this setup:
1. MongoDB v2.6 – v3.2 have reached their End of Life already (v2.6 almost 3
years ago!). See the "MongoDB Server" section on
https://www.mongodb.com/support-policy.
2. We were only testing two recent-ish PyMongo versions (v3.5.0 & v3.6.1).
We were not testing the oldest actively supported MongoDB/PyMongo/Python
setup.
This PR updates the test matrix so that these problems are solved. For the
sake of simplicity, it does not yet attempt to cover MongoDB v4.0:
- PyPy, MongoDB v3.4, PyMongo v3.x (aka v3.6.1 at the moment)
- Python v2.7, MongoDB v3.4, PyMongo v3.x
- Python v3.5, MongoDB v3.4, PyMongo v3.x
- Python v3.6, MongoDB v3.4, PyMongo v3.x
- Python v2.7, MongoDB v3.4, PyMongo v3.4
- Python v3.6, MongoDB v3.6, PyMongo v3.x
