Revise Playlist Extraction to YouTubes architecture changes (#805)

* Revise playlist extraction

* Regenerated playlist_long mock

* Adjusted unit test to account for changes

pytube/contrib/playlist.py

@@ -179,21 +179,24 @@ class Playlist(Sequence):
             ][
                 "playlistVideoListRenderer"
             ]
+            videos = important_content["contents"]
         except (KeyError, IndexError, TypeError):
             try:
                 # this is the json tree structure, if the json was directly sent
                 # by the server in a continuation response
-                important_content = initial_data[1]["response"][
-                    "continuationContents"
-                ]["playlistVideoListContinuation"]
+                important_content = initial_data[1]['response']['onResponseReceivedActions'][
+                    0
+                ]['appendContinuationItemsAction']['continuationItems']
+                videos = important_content
             except (KeyError, IndexError, TypeError) as p:
                 print(p)
                 return [], None
-        videos = important_content["contents"]
+
         try:
-            continuation = important_content["continuations"][0][
-                "nextContinuationData"
-            ]["continuation"]
+            continuation = videos[-1]['continuationItemRenderer'][
+                'continuationEndpoint'
+            ]['continuationCommand']['token']
+            videos = videos[:-1]
         except (KeyError, IndexError):
             # if there is an error, no continuation is available
             continuation = None

tests/contrib/test_playlist.py

@@ -224,7 +224,7 @@ def test_trimmed_pagination(request_get, playlist_html, playlist_long_html):
         "{}",
     ]
     playlist = Playlist(url)
-    assert len(list(playlist.trimmed("Gj6fv4pvUwM"))) == 3
+    assert len(list(playlist.trimmed("GTpl5yq3bvk"))) == 3
     assert request_get.call_count == 1