Put back template_name on proxito 404 view

We are overriding it on .com, it probably isn't necessary since we
aren't using it in the view, but I'm adding it back just for sake of
deploy.

Author: stsewd

readthedocs/proxito/views/serve.py

@@ -472,7 +472,8 @@ class ServeError404Base(CDNCacheControlMixin, ServeRedirectMixin, ServeDocsMixin
     This view is called by an internal nginx redirect when there is a 404.
     """
 
-    def get(self, request, proxito_path):
+    # pylint: disable=unused-argument
+    def get(self, request, proxito_path, template_name="404.html"):
         """
         Handler for 404 pages on subdomains.