Add python 3.9 to tests matrix #2371

	name: Style checks

	on:
	push:
	pull_request:

	jobs:
	build:
	runs-on: ubuntu-latest
	strategy:
	max-parallel: 4
	matrix:
	python-version: [3.8]
	environment: [style, black]

	steps:
	- uses: actions/checkout@v1
	- name: Set up Python ${{ matrix.python-version }}
	uses: actions/setup-python@v2
	with:
	python-version: ${{ matrix.python-version }}
	- name: Install dependencies
	run: \|
	python -m pip install --upgrade pip
	pip install tox==4.2.6
	- name: Test with tox
	run: tox -e ${{ matrix.environment }}

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