YouTube RSS feed endpoint returns HTTP 200 status code but serves Google's 404 error HTML page as the body for some channels during outage windows. Code that only checks HTTP status codes (e.g., curl -f, requests.raise_for_status()) will incorrectly treat these as successful responses and parse garbage HTML instead of Atom XML.
Always validate the response body starts with '<?xml' or contains '<feed xmlns' before treating a YouTube RSS response as valid, regardless of HTTP status code. The load balancer returns 200 when the backend serving feeds is dead, proxying the error page without propagating the error status.