Update actions/checkout action to v4 #316

	name: build

	on: [push]

	jobs:
	build:
	runs-on: ${{ matrix.os }}
	strategy:
	matrix:
	os: [ubuntu-latest, macos-latest]
	python-version: [3.6, 3.7, 3.8]
	exclude:
	- os: macos-latest
	python-version: 3.8

	steps:
	- uses: actions/checkout@v4
	- name: Set up Python 3.7
	uses: actions/setup-python@v3
	with:
	python-version: 3.7
	- uses: actions/checkout@v4.1.3
	- uses: julia-actions/setup-julia@v1
	with:
	version: '1.4.1'
	- name: Install Julia dependencies
	run: \|
	julia --color=yes -e 'using Pkg; Pkg.add(Pkg.PackageSpec(path="https://github.com/APLA-Toolbox/PDDL.jl"))'
	julia --color=yes -e 'using Pkg; Pkg.add(Pkg.PackageSpec(path="https://github.com/JuliaPy/PyCall.jl"))'
	- name: Install Python dependencies
	run: \|
	python -m pip install --upgrade pip
	python -m pip install -r requirements.txt
	- name: Lint with flake8
	run: \|
	python -m pip install flake8
	# stop the build if there are Python syntax errors or undefined names
	flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
	# exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
	flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
	- name: Checkout reposistory
	uses: actions/checkout@master
	- name: Checkout submodules
	uses: snickerbockers/submodules-init@v4

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