test: ignore E501 error for flake8 check

Author: ferstar

tox.ini

@@ -15,7 +15,7 @@ commands = pytest --ignore=tests/test_benchmark.py
 basepython = python3
 deps =
      flake8
-commands = flake8 {toxinidir} --extend-exclude tests,docs,build,dist,venv
+commands = flake8 {toxinidir} --extend-exclude tests,docs,build,dist,venv --extend-ignore=E501
 
 [testenv:doc]
 basepython = python3