[youtube:channel] Fix automated channel detection

youtube_dl/extractor/youtube.py

@@ -1631,10 +1631,11 @@ class YoutubeChannelIE(InfoExtractor):
         video_ids = []
         url = 'https://www.youtube.com/channel/%s/videos' % channel_id
         channel_page = self._download_webpage(url, channel_id)
-        if re.search(r'channel-header-autogenerated-label', channel_page) is not None:
-            autogenerated = True
-        else:
-            autogenerated = False
+        autogenerated = re.search(r'''(?x)
+                class="[^"]*?(?:
+                    channel-header-autogenerated-label|
+                    yt-channel-title-autogenerated
+                )[^"]*"''', channel_page) is not None
 
         if autogenerated:
             # The videos are contained in a single page