flake8-polyfill setup.cfg is incompatible with pytest versions >= 4.0

[sigmavirus24]

In GitLab by @detrout on Mar 1, 2020, 23:57

pytest depreciated using [pytest] in the setup.cfg and requires using [tool:pytest] instead. This was causing debian bug https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=951977

See the following for the deprecation notice.
https://docs.pytest.org/en/latest/deprecations.html#pytest-section-in-setup-cfg-files

This patch fixes the pytest error.

--- a/setup.cfg
+++ b/setup.cfg
@@ -1,7 +1,7 @@
 [bdist_wheel]
 universal = 1
 
-[pytest]
+[tool:pytest]
 norecursedirs = .git .* *.egg* old docs dist build
 addopts = -rw