run-tests: rename "pure" variable to setup_opts
There are more useful flag than just `--pure`. We clarify the variable name
before adding more options.
[tool.black]
line-length = 80
exclude = '''
build/
| wheelhouse/
| dist/
| packages/
| \.hg/
| \.mypy_cache/
| \.venv/
| mercurial/thirdparty/
'''
skip-string-normalization = true
quiet = true