Fix annoying pip dep resolution issue

with flake8>=3.5.0 and autopep8>=1.3.5, pycodestyle should resolve to
2.3.1. Instead, it resolves to 2.4.0 when you use `pip install -r
requirements_dev.txt`. But, when you use `pip install 'flake8>=3.5.0'
'autopep8>=1.3.5'`, the correct resolution of 2.3.1 occurs. No idea what
is going on.

Author: micahjsmith

requirements_dev.txt

@@ -2,5 +2,6 @@ autoflake
 autopep8>=1.3.5
 flake8>=3.5.0
 isort
+pycodestyle<2.4.0
 
 -r requirements_test.txt