Fixes issue with playlist not loading urls sometimes. (#860)

* Updated extract.initial_data to account for variety in locations.

pytube/extract.py

@@ -457,11 +457,17 @@ def initial_data(watch_html: str) -> str:
     @param watch_html: Html of the watch page
     @return:
     """
-    initial_data_pattern = r"window\[['\"]ytInitialData['\"]]\s*=\s*"
-    try:
-        return parse_for_object(watch_html, initial_data_pattern)
-    except HTMLParseError:
-        return {}
+    patterns = [
+        r"window\[['\"]ytInitialData['\"]]\s*=\s*",
+        r"ytInitialData\s*=\s*"
+    ]
+    for pattern in patterns:
+        try:
+            return parse_for_object(watch_html, pattern)
+        except HTMLParseError:
+            pass
+
+    raise RegexMatchError(caller="initial_data", pattern='initial_data_pattern')
 
 
 def initial_player_response(watch_html: str) -> str:

tests/test_extract.py

@@ -105,8 +105,8 @@ def test_signature_cipher_does_not_error(stream_dict):
 
 
 def test_initial_data_missing():
-    initial_data = extract.initial_data('')
-    assert initial_data == {}
+    with pytest.raises(RegexMatchError):
+        extract.initial_data('')
 
 
 def test_initial_data(stream_dict):

tests/test_helpers.py

@@ -121,7 +121,7 @@ def test_create_mock_html_json(mock_url_open, mock_open):
     # 2. vid_info_raw
     # 3. js
     mock_url_open_object.read.side_effect = [
-        (b'yt.setConfig({"PLAYER_CONFIG":{"args":[]}});'
+        (b'yt.setConfig({"PLAYER_CONFIG":{"args":[]}});ytInitialData = {}'
          b'"jsUrl":"/s/player/13371337/player_ias.vflset/en_US/base.js"'),
         b'vid_info_raw',
         b'js_result',