test_global_config.py has a usage example

Just fix tests to use Factory instead of old style

It seems that the typing module doesn't flatten nested literal type definitions, so the following does not currently work:

SuccessStatus = Literal[200, 201, 204]
ClientError = Literal[404, 401, 403, 409, 400]
ServerError = Literal[500, 504, 503]

@dataclass
class HttpResponse(JsonSchemaMixin):
    status: Literal[SuccessStatus, ClientError, ServerError]
    ...

https://docs.python.org/3/reference/datamodel.html#object.__bytes__

Mypy fails on desert currently.