[youtube] Do not warn for videos with allow_rating=0

This fixes #1982
Test video: http://www.youtube.com/watch?v=gi2uH3YxohU

youtube_dl/extractor/common.py

@@ -18,6 +18,7 @@
     sanitize_filename,
     unescapeHTML,
 )
+_NO_DEFAULT = object()
 
 
 class InfoExtractor(object):
@@ -281,7 +282,7 @@ def playlist_result(self, entries, playlist_id=None, playlist_title=None):
             video_info['title'] = playlist_title
         return video_info
 
-    def _search_regex(self, pattern, string, name, default=None, fatal=True, flags=0):
+    def _search_regex(self, pattern, string, name, default=_NO_DEFAULT, fatal=True, flags=0):
         """
         Perform a regex search on the given string, using a single or a list of
         patterns returning the first matching group.
@@ -303,7 +304,7 @@ def _search_regex(self, pattern, string, name, default=None, fatal=True, flags=0
         if mobj:
             # return the first matching group
             return next(g for g in mobj.groups() if g is not None)
-        elif default is not None:
+        elif default is not _NO_DEFAULT:
             return default
         elif fatal:
             raise RegexNotFoundError(u'Unable to extract %s' % _name)
@@ -312,7 +313,7 @@ def _search_regex(self, pattern, string, name, default=None, fatal=True, flags=0
                 u'please report this issue on http://yt-dl.org/bug' % _name)
             return None
 
-    def _html_search_regex(self, pattern, string, name, default=None, fatal=True, flags=0):
+    def _html_search_regex(self, pattern, string, name, default=_NO_DEFAULT, fatal=True, flags=0):
         """
         Like _search_regex, but strips HTML tags and unescapes entities.
         """

youtube_dl/extractor/xtube.py

@@ -32,7 +32,7 @@ def _real_extract(self, url):
 
         video_title = self._html_search_regex(r'<div class="p_5px[^>]*>([^<]+)', webpage, u'title')
         video_uploader = self._html_search_regex(r'so_s\.addVariable\("owner_u", "([^"]+)', webpage, u'uploader', fatal=False)
-        video_description = self._html_search_regex(r'<p class="video_description">([^<]+)', webpage, u'description', default=None)
+        video_description = self._html_search_regex(r'<p class="video_description">([^<]+)', webpage, u'description', fatal=False)
         video_url= self._html_search_regex(r'var videoMp4 = "([^"]+)', webpage, u'video_url').replace('\\/', '/')
         path = compat_urllib_parse_urlparse(video_url).path
         extension = os.path.splitext(path)[1][1:]

youtube_dl/extractor/youtube.py

@@ -1361,7 +1361,9 @@ def _real_extract(self, url):
                 video_description = u''
 
         def _extract_count(klass):
-            count = self._search_regex(r'class="%s">([\d,]+)</span>' % re.escape(klass), video_webpage, klass, fatal=False)
+            count = self._search_regex(
+                r'class="%s">([\d,]+)</span>' % re.escape(klass),
+                video_webpage, klass, default=None)
             if count is not None:
                 return int(count.replace(',', ''))
             return None