Update flake8 to 3.9.0#1343

pyup-bot wants to merge 1 commit intomastermohankishore/python_dynamodb_lock:masterfrom

pyup-update-flake8-3.7.7-to-3.9.0mohankishore/python_dynamodb_lock:pyup-update-flake8-3.7.7-to-3.9.0Copy head branch name to clipboard