Keyword only args causes RequestMiddleware to fail on Django app load

[bradykieffer]

Environment details

• OS type and version: macOS version 11.0.1
• Python version: Python 3.8.2
• pip version: pip 20.2.4
• google-cloud-logging version: 2.0.1 and 2.0.0

Steps to reproduce

1. Add google.cloud.logging_v2.handlers.middleware.RequestMiddleware to a MIDDLEWARE list in django app settings
2. Make an API request, e.g. during a test

Stack trace

self = <django.test.client.ClientHandler object at 0x124a5f850>

    def load_middleware(self):
        """
        Populate middleware lists from settings.MIDDLEWARE.

        Must be called after the environment is fixed (see __call__ in subclasses).
        """
        self._view_middleware = []
        self._template_response_middleware = []
        self._exception_middleware = []

        handler = convert_exception_to_response(self._get_response)
        for middleware_path in reversed(settings.MIDDLEWARE):
            middleware = import_string(middleware_path)
            try:
>               mw_instance = middleware(handler)
E               TypeError: __init__() takes 1 positional argument but 2 were given

Extra Info

It looks like django doesn't support keyword only arguments when loading middleware (the link is pointing to master, but it's the same for old versions). If I locally do the following, I can subclass the RequestMiddleware and remove the keyword only args and the whole issue goes away

[bradykieffer]

A colleague of mine pointed out that this issue is related to the 2.0.0 update. Looking at Django's docs for 3.1 and 2.2 it doesn't seem like get_response is an optional, we could default it to non-null to fix this issue.