DOC: build with Sphinx version 4 #536

	name: Build docs and check links
	on: [push, pull_request]
	env:
	PYTHONWARNINGS: error
	PIP: python -m pip
	SPHINX: python -m sphinx -W --keep-going --color
	jobs:
	docs:
	runs-on: ubuntu-latest
	steps:
	- name: Clone repo
	uses: actions/checkout@v3
	with:
	fetch-depth: 0
	submodules: true
	- name: Set up Python
	uses: actions/setup-python@v4
	with:
	python-version: "3"
	- name: Double-check Python version
	run: \|
	python --version
	- name: Install Python package
	env:
	PYTHONWARNINGS: error,default::DeprecationWarning
	run: \|
	$PIP install .
	- name: Install docs dependencies
	env:
	PYTHONWARNINGS: error,default::DeprecationWarning
	run: \|
	$PIP install -r doc/requirements.txt
	- name: Build HTML
	run: \|
	$SPHINX -d _build/doctrees/ doc/ _build/html/ -b html
	- name: Upload error log
	uses: actions/upload-artifact@v3
	if: failure()
	with:
	name: build-log
	path: /tmp/sphinx-err-*.log
	- name: Check links
	run: \|
	$SPHINX -d _build/doctrees/ doc/ _build/linkcheck/ -b linkcheck
	- name: Upload linkcheck results
	uses: actions/upload-artifact@v3
	if: ${{ success() \|\| failure() }}
	with:
	name: linkcheck
	path: _build/linkcheck/output.*

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