Make flattentool dependency optional (aka add PyPy support for use cases not requiring flattentool) #278

	name: Test
	on: [push, pull_request]
	jobs:
	build:
	runs-on: ${{ matrix.os }}
	strategy:
	matrix:
	# libcove doesn't support Windows.
	# https://github.com/OpenDataServices/lib-cove/issues/53
	# We also only use Linux servers, so don't test on Mac
	# Need to use an older Ubuntu so Python 3.6 is available
	os: [ubuntu-20.04]
	python-version: [ 3.6, 3.7, 3.8, 3.9, "3.10", "3.11" ]
	jsonref-version: ["==0.3", ">1"]
	steps:
	- uses: actions/checkout@v2
	- uses: actions/setup-python@v1
	with:
	python-version: ${{ matrix.python-version }}
	- name: Install
	run: \|
	pip install -r requirements_dev.txt
	pip install .
	pip install 'jsonref${{ matrix.jsonref-version }}'
	- name: Test
	run: py.test tests/
	- name: Install with flatten requirement specifier
	run: pip install .[flatten]
	- name: Test with flatten requirement specifier
	run: py.test tests/

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