ignore user python packages by using `-s` option when running Python code via `python -c` #4038

	name: Static Analysis
	on: [push, pull_request]

	permissions:
	contents: read # to fetch code (actions/checkout)

	concurrency:
	group: ${{format('{0}:{1}:{2}', github.repository, github.ref, github.workflow)}}
	cancel-in-progress: true

	jobs:
	python-linting:
	runs-on: ubuntu-20.04
	steps:
	- uses: actions/checkout@v2

	- name: set up Python
	uses: actions/setup-python@v2
	with:
	python-version: 3.8

	- name: install Python packages
	run: \|
	pip install --upgrade pip
	# fix to this version for develop branch (to avoid needing to fix geant4.py)
	pip install --upgrade "flake8"

	- name: Run flake8 to verify PEP8-compliance of Python code
	run: flake8

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