Only test `register_handler` in a single thread #9567

	name: Lint

	on: [push, pull_request, workflow_dispatch]

	env:
	FORCE_COLOR: 1

	permissions:
	contents: read

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

	jobs:
	build:

	runs-on: ubuntu-latest

	name: Lint

	steps:
	- uses: actions/checkout@v4

	- name: pre-commit cache
	uses: actions/cache@v4
	with:
	path: ~/.cache/pre-commit
	key: lint-pre-commit-${{ hashFiles('**/.pre-commit-config.yaml') }}
	restore-keys: \|
	lint-pre-commit-

	- name: Set up Python
	uses: actions/setup-python@v5
	with:
	python-version: "3.x"
	cache: pip
	cache-dependency-path: "setup.py"

	- name: Build system information
	run: python3 .github/workflows/system-info.py

	- name: Install dependencies
	run: \|
	python3 -m pip install -U pip
	python3 -m pip install -U tox

	- name: Lint
	run: tox -e lint
	env:
	PRE_COMMIT_COLOR: always

	- name: Mypy
	run: tox -e mypy

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