[YoutubeDL] More error_to_str

youtube_dl/YoutubeDL.py

@@ -1511,7 +1511,7 @@ class YoutubeDL(object):
                             sub_info['url'], info_dict['id'], note=False)
                     except ExtractorError as err:
                         self.report_warning('Unable to download subtitle for "%s": %s' %
-                                            (sub_lang, compat_str(err.cause)))
+                                            (sub_lang, error_to_str(err.cause)))
                         continue
                 try:
                     sub_filename = subtitles_filename(filename, sub_lang, sub_format)