flake8: Fix all warnings in api app
flake8: Fix all warnings in accounts app
flake8: Fix all warnings in top-level urlconf
flake8: Fix all warnings in status app
flake8: Fix all warnings in aggregator app
flake8: Fix all warnings in help app
flake8: Fix all warnings in browser app
flake8: Fix all warnings in sets app
flake8: Fix all warnings in core app (except migrations)
flake8: Fix all warnings in comics crawlers