lint: Bump flake8 to 3.7.8
lint: Bump flake8 to 3.7.8

Former-commit-id: f8fdbc48b46401a16c3f5f237cf1394de9a04ef6
syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin