python: Add basic openapi.json fetching test

python/tests/test_client.py

@@ -1,4 +1,5 @@
 import itertools
+import requests
 import uuid
 from typing import Any, Dict, List, Optional
 
@@ -234,3 +235,9 @@ def webhook_handler(request: Request) -> Response:
     assert message_out.event_type == event_type.name
     if with_channel:
         assert message_out.channels == [channel]
+
+
+def test_openapi_json_is_available(svix_server_url: str) -> None:
+    r = requests.get("{svix_server_url}/openapi.json")
+    assert r.status_code == 200
+    assert r.headers["content-type"] == 'application/json; charset=utf8'