- Split out tests and add markers to control where they are run in Travis
- Run each marker on a separate Travis task
- Install pytest-xdist to increase parallelism inside each worker
- Set xdist parallelism to 3
* Create a test matrix on Travis CI to help testing multiple options
* Change test_docker.sh to fail if any command in it fails
* Run black on the CI with --check option
* Fix formatting of project files using black
* Install black in the docker container
* Exclude migrations in black checks
* Fix Black formatting violations
* Run black on the whole generated project & fix issues
* Convert old-styled string formatting to f-string
* Update flake8 explicit version to 3.5.0
* Make tox.ini in sync with requirements.txt
* Fix annoying flake8 F405
