[youtube] Extract precise error messages (closes #15284)

ChangeLog

@@ -1,3 +1,10 @@
+version <unreleased>
+
+Extractors
+
+* [youtube] Extract precise error messages (#15284)
+
+
 version 2018.01.21
 
 Core

youtube_dl/extractor/youtube.py

@@ -1596,6 +1596,12 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                         if 'token' not in video_info:
                             video_info = get_video_info
                         break
+
+        def extract_unavailable_message():
+            return self._html_search_regex(
+                r'(?s)<h1[^>]+id="unavailable-message"[^>]*>(.+?)</h1>',
+                video_webpage, 'unavailable message', default=None)
+
         if 'token' not in video_info:
             if 'reason' in video_info:
                 if 'The uploader has not made this video available in your country.' in video_info['reason']:
@@ -1604,8 +1610,13 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                     countries = regions_allowed.split(',') if regions_allowed else None
                     self.raise_geo_restricted(
                         msg=video_info['reason'][0], countries=countries)
+                reason = video_info['reason'][0]
+                if 'Invalid parameters' in reason:
+                    unavailable_message = extract_unavailable_message()
+                    if unavailable_message:
+                        reason = unavailable_message
                 raise ExtractorError(
-                    'YouTube said: %s' % video_info['reason'][0],
+                    'YouTube said: %s' % reason,
                     expected=True, video_id=video_id)
             else:
                 raise ExtractorError(
@@ -1953,9 +1964,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
                 a_format.setdefault('http_headers', {})['Youtubedl-no-compression'] = 'True'
                 formats.append(a_format)
         else:
-            unavailable_message = self._html_search_regex(
+            unavailable_message = extract_unavailable_message()
-                r'(?s)<h1[^>]+id="unavailable-message"[^>]*>(.+?)</h1>',
-                video_webpage, 'unavailable message', default=None)
             if unavailable_message:
                 raise ExtractorError(unavailable_message, expected=True)
             raise ExtractorError('no conn, hlsvp or url_encoded_fmt_stream_map information found in video info')