Bump flake8 from 3.8.3 to 3.8.4

Bumps [flake8](https://gitlab.com/pycqa/flake8) from 3.8.3 to 3.8.4.
- [Release notes](https://gitlab.com/pycqa/flake8/tags)
- [Commits](https://gitlab.com/pycqa/flake8/compare/3.8.3...3.8.4)

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

Author: dependabot[bot]

poetry.lock

@@ -32,7 +32,7 @@ django = ">=2.0"
 
 [tool.poetry.dev-dependencies]
 black = "^20.8b1"
-flake8 = "^3.8.3"
+flake8 = "^3.8.4"
 flake8-bandit = "^2.1.2"
 flake8-bugbear = "^20.1.4"
 safety = "^1.8.5"