Refactor code to comply with flake8 and isort

aurweb/git/auth.py

aurweb/git/serve.py

aurweb/git/update.py

aurweb/initdb.py

aurweb/l10n.py

aurweb/schema.py

aurweb/scripts/aurblup.py

aurweb/scripts/rendercomment.py

migrations/env.py

schema/gendummydata.py

setup.py