youtube: Fix for HTTPError stub change.

https://github.com/python/typeshed/pull/10875

Signed-off-by: Anders Kaseorg <anders@zulip.com>

zulip_bots/zulip_bots/bots/youtube/youtube.py

@@ -34,6 +34,7 @@ class YoutubeHandler:
         try:
             search_youtube("test", self.config_info["key"], self.config_info["video_region"])
         except HTTPError as e:
+            assert e.response is not None
             if e.response.json()["error"]["errors"][0]["reason"] == "keyInvalid":
                 bot_handler.quit(
                     "Invalid key." "Follow the instructions in doc.md for setting API key."