Refactoring between 3.3.3 and 3.4.0 changed how Response.render passes media_type to its renderer.

Response sets it as media_type = renderer.media_type compared to self.accepted_media_type (set via APIView.finalize_response here).

Since renderer.media_type looses the indent parameter (i.e. application/json; indent=4 becomes application/json), the resulting JSON rendering is not indented.

A 'simple' fix is to restore the 3.3.3 code where media_type = getattr(self, 'accepted_media_type', None) but I haven't made a PR yet because I'm not clear as to whether there was a specific reason for changing to renderer.media_type (which might have overlooked that it doesn't include indent).