fix(django): SentryWrappingMiddleware.__init__ fails if super() is object

As described in issue #2461, the SentryWrappingMiddleware MRO is just object if Django < 3.1 (when async middleware became a thing), but the async_capable check inside the class only looks for the async_capable attribute inside the middleware class.

This PR makes that check also conditional on Django >= 3.1.

Otherwise the code calls super(.....).__init__(get_response) and for Django < 3.1 this only finds object.__init__, not the wrapped middleware __init__.

---

Co-authored-by: Daniel Szoke <[email protected]>

Author: cameron-simpson

sentry_sdk/integrations/django/middleware.py

@@ -30,7 +30,9 @@
     "import_string_should_wrap_middleware"
 )
 
-if DJANGO_VERSION < (3, 1):
+DJANGO_SUPPORTS_ASYNC_MIDDLEWARE = DJANGO_VERSION >= (3, 1)
+
+if not DJANGO_SUPPORTS_ASYNC_MIDDLEWARE:
     _asgi_middleware_mixin_factory = lambda _: object
 else:
     from .asgi import _asgi_middleware_mixin_factory
@@ -123,7 +125,9 @@ def sentry_wrapped_method(*args, **kwargs):
     class SentryWrappingMiddleware(
         _asgi_middleware_mixin_factory(_check_middleware_span)  # type: ignore
     ):
-        async_capable = getattr(middleware, "async_capable", False)
+        async_capable = DJANGO_SUPPORTS_ASYNC_MIDDLEWARE and getattr(
+            middleware, "async_capable", False
+        )
 
         def __init__(self, get_response=None, *args, **kwargs):
             # type: (Optional[Callable[..., Any]], *Any, **Any) -> None