Avoid `RemovedInSphinx80Warning` in path-manipulation code. #913

	name: lint
	on: [push, pull_request]
	jobs:
	build:

	runs-on: ubuntu-latest

	steps:
	- uses: actions/checkout@v2
	- uses: actions/cache@v1
	with:
	path: ~/.cache/pip
	key: ${{ runner.os }}-pip-${{ hashFiles('requirements/*.txt') }}
	restore-keys: \|
	${{ runner.os }}-pip-
	- name: set up python
	uses: actions/setup-python@v1

	- name: install dependencies
	run: \|
	pip install -r requirements/development.txt

	- name: lint the source code
	run: make flake8

	- name: check source code formatting
	run: make black

	- name: type check the source code
	run: make type-check

	- name: check version numbers are in sync
	run: make version-check

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