[youtube] Correct signature extraction error detection

youtube_dl/extractor/youtube.py

@@ -865,7 +865,9 @@ class YoutubeIE(YoutubeBaseInfoExtractor, SubtitlesInfoExtractor):
     def _decrypt_signature(self, s, video_id, player_url, age_gate=False):
         """Turn the encrypted s field into a working signature"""
 
-        if player_url is not None:
+        if player_url is None:
+            raise ExtractorError(u'Cannot decrypt signature without player_url')
+
         if player_url.startswith(u'//'):
             player_url = u'https:' + player_url
         try:
@@ -884,9 +886,6 @@ class YoutubeIE(YoutubeBaseInfoExtractor, SubtitlesInfoExtractor):
             raise ExtractorError(
                 u'Automatic signature extraction failed: ' + tb, cause=e)
 
-        return self._static_decrypt_signature(
-            s, video_id, player_url, age_gate)
-
     def _get_available_subtitles(self, video_id, webpage):
         try:
             sub_list = self._download_webpage(