Bump flake8 from 3.7.9 to 3.8.1

Bumps [flake8](https://gitlab.com/pycqa/flake8) from 3.7.9 to 3.8.1.
- [Release notes](https://gitlab.com/pycqa/flake8/tags)
- [Commits](https://gitlab.com/pycqa/flake8/compare/3.7.9...3.8.1)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Author: dependabot-preview[bot]

setup.py

@@ -23,7 +23,7 @@
     + FRAMEWORKS,
     "lint": [
         "mypy==0.770",
-        "flake8==3.7.9",
+        "flake8==3.8.1",
         "flake8-bugbear==20.1.4",
         "pre-commit>=1.20,<3.0",
     ],