Add extend-select to flake8 #922

	name: Static code analysis

	on:
	push:
	branches:
	- develop

	pull_request:
	branches:
	- '*'

	concurrency:
	group: static-${{ github.ref }}
	cancel-in-progress: true

	jobs:
	build:
	name: Static code analysis
	runs-on: ubuntu-latest
	env:
	CI: 'true'
	OS: 'linux'
	timeout-minutes: 2
	steps:
	- uses: actions/cache@v1
	with:
	path: ~/.cache/pip
	key: static-pip-${{ hashFiles('pyproject.toml') }}
	restore-keys: static-pip-
	- uses: actions/checkout@v2
	- uses: actions/setup-python@v2
	with:
	# TODO: check with Python 3, but need to fix the
	# errors first
	python-version: '3.8'
	architecture: 'x64'
	- run: python -m pip install --upgrade pip setuptools jsonschema
	# If we don't install pycodestyle, pylint will throw an unused-argument error in pylsp/plugins/pycodestyle_lint.py:72
	# This error cannot be resolved by adding a pylint: disable=unused-argument comment ...
	- run: \|
	pip install -e .[pylint,pycodestyle]
	pip install ruff
	- name: ruff linter and code style checks
	run: ruff check pylsp test
	- name: ruff code formatter check
	run: ruff format --check pylsp test
	- name: Validate JSON schema
	run: echo {} \| jsonschema pylsp/config/schema.json
	- name: Ensure JSON schema and Markdown docs are in sync
	run: \|
	python scripts/jsonschema2md.py pylsp/config/schema.json EXPECTED_CONFIGURATION.md
	diff EXPECTED_CONFIGURATION.md CONFIGURATION.md

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