bump version to `0.21.0` (#378) #862

	name: format
	on:
	pull_request:
	push:
	branches:
	- master

	jobs:
	black:
	runs-on: ubuntu-latest
	steps:
	- name: Cancel Previous Runs
	uses: styfle/[email protected]
	with:
	access_token: ${{ github.token }}

	- name: Set up Python
	uses: actions/setup-python@v2
	with:
	python-version: 3.7

	- name: Install dependencies
	run:
	python -m pip install --upgrade pip
	pip install black

	- uses: actions/checkout@v2

	- name: Run Black
	run: black -l 100 thewalrus/ --check

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