Drops Py3.7, improves typing and adds a mypy config, improves the docstrings and isorts the imports.
* configure isort
* sort with isort
* add github action
* enable flake8-docstrings
* fix docstrings
* add mypy env
* no implicit optional
* add type for raw
* add some type hints
Python 2.7 EOL is arriving on 2020-01-01: https://pythonclock.org/
This will allow us to use Python 3 only libraries, like python-barcode,
which can maintain a reduced, simpler codebase, due to only one version
to support.
Closes#371.
Signed-off-by: Romain Porte <microjoe@microjoe.org>
