Fixed #26504 -- Avoided logging "Not Found" warnings if a middleware handles the 404.

For example, this avoids a warning in the case of a request that's
redirected to a language-prefixed URL by LocaleMiddleware.

django/core/handlers/base.py

@@ -179,10 +179,6 @@ class BaseHandler(object):
                 response_is_rendered = True
 
         except http.Http404 as exc:
-            logger.warning(
-                'Not Found: %s', request.path,
-                extra={'status_code': 404, 'request': request},
-            )
             if settings.DEBUG:
                 response = debug.technical_404_response(request, exc)
             else:
@@ -246,6 +242,12 @@ class BaseHandler(object):
         if not response_is_rendered and callable(getattr(response, 'render', None)):
             response = response.render()
 
+        if response.status_code == 404:
+            logger.warning(
+                'Not Found: %s', request.path,
+                extra={'status_code': 404, 'request': request},
+            )
+
         return response
 
     def process_exception_by_middleware(self, exception, request):