[youtube] Extract error messages from HTTPError response (#644)

Authored by: coletdjnz

yt_dlp/extractor/youtube.py

@@ -38,6 +38,7 @@ from ..utils import (
     format_field,
     int_or_none,
     intlist_to_bytes,
+    is_html,
     mimetype2ext,
     network_exceptions,
     orderedSet,
@@ -723,11 +724,11 @@ class YoutubeBaseInfoExtractor(InfoExtractor):
                 if message:
                     yield alert_type, message
 
-    def _report_alerts(self, alerts, expected=True):
+    def _report_alerts(self, alerts, expected=True, fatal=True):
         errors = []
         warnings = []
         for alert_type, alert_message in alerts:
-            if alert_type.lower() == 'error':
+            if alert_type.lower() == 'error' and fatal:
                 errors.append([alert_type, alert_message])
             else:
                 warnings.append([alert_type, alert_message])
@@ -793,6 +794,13 @@ class YoutubeBaseInfoExtractor(InfoExtractor):
                     note='%s%s' % (note, ' (retry #%d)' % count if count else ''))
             except ExtractorError as e:
                 if isinstance(e.cause, network_exceptions):
+                    if isinstance(e.cause, compat_HTTPError) and not is_html(e.cause.read(512)):
+                        e.cause.seek(0)
+                        yt_error = try_get(
+                            self._parse_json(e.cause.read().decode(), item_id, fatal=False),
+                            lambda x: x['error']['message'], compat_str)
+                        if yt_error:
+                            self._report_alerts([('ERROR', yt_error)], fatal=False)
                     # Downloading page may result in intermittent 5xx HTTP error
                     # Sometimes a 404 is also recieved. See: https://github.com/ytdl-org/youtube-dl/issues/28289
                     # We also want to catch all other network exceptions since errors in later pages can be troublesome