Add workaround for DeprecationWarning in flake8
@@ -7,3 +7,5 @@ filterwarnings=
ignore:Using or importing the ABCs::flake8:410
# workaround for https://sourceforge.net/p/docutils/bugs/348/
ignore:'U' mode is deprecated::docutils.io
+ # workaround for https://gitlab.com/pycqa/flake8/issues/275
+ ignore:You passed a bytestring as `filenames`.::flake8
