Avoid generating singleton Unions

Author: nkrishnaswami

end_to_end_tests/multiple-media-types-golden-record/multiple_media_types_client/api/multiple_media_types/post.py

@@ -36,6 +36,12 @@ def _parse_response(
             response_200 = cast(Any, response.content)
             return response_200
 
+    if response.status_code == 404:
+        response_404: Any
+        if response.headers.get("content-type") == "text/plain":
+            response_404 = cast(Any, response.text)
+            return response_404
+
     if response.status_code == 503:
         response_503: ErrorResponse | Any
         if response.headers.get("content-type") == "application/json":

end_to_end_tests/multiple-media-types.yml

@@ -15,6 +15,10 @@ paths:
               schema:
                 const: "Why have a fixed response? I dunno"
             "application/octet-stream": {}
+        "404":
+          description: "Not Found"
+          content:
+            "text/plain": {}
         "503":
           description: "Server Not Available"
           content: