Merge pull request #3404 from django-oscar/dependabot/pip/flake8-3.8.3

Bump flake8 from 3.8.2 to 3.8.3

requirements.txt

 whitenoise==5.1.0
 
 # Linting
-flake8==3.8.2
+flake8==3.8.3
 flake8-debugger==3.2.1
 flake8-blind-except==0.1.1
 isort==4.3.21