Adding “Black” the Excellent Python Code Formatter to Pre-Commit

Add the following to your .pre-commit-config.yaml. WARNING: black isn’t compatible with add-trailing-comma or add-trailing-comma hooks!
- repo: https://github.com/ambv/black
rev: 18.6b2
hooks:
- id: black
args: [--line-length=79, --safe]
python_version: python3.6