[videolecturesnet] Add support for playlists (Closes #7031)

youtube_dl/extractor/videolecturesnet.py

@@ -1,9 +1,10 @@
 from __future__ import unicode_literals
 
+import re
+
 from .common import InfoExtractor
-from ..utils import (
-    parse_duration,
-)
+from ..compat import compat_urlparse
+from ..utils import parse_duration
 
 
 class VideoLecturesNetIE(InfoExtractor):
@@ -27,7 +28,17 @@ class VideoLecturesNetIE(InfoExtractor):
         video_id = self._match_id(url)
 
         smil_url = 'http://videolectures.net/%s/video/1/smil.xml' % video_id
-        smil = self._download_smil(smil_url, video_id)
+        smil = self._download_smil(smil_url, video_id, fatal=False)
+
+        # Probably a playlist
+        if smil is False:
+            webpage = self._download_webpage(url, video_id)
+            entries = [
+                self.url_result(compat_urlparse.urljoin(url, video_url), 'VideoLecturesNet')
+                for _, video_url in re.findall(r'<a[^>]+href=(["\'])(.+?)\1[^>]+id=["\']lec=\d+', webpage)]
+            playlist_title = self._html_search_meta('title', webpage, 'title', fatal=True)
+            playlist_description = self._html_search_meta('description', webpage, 'description')
+            return self.playlist_result(entries, video_id, playlist_title, playlist_description)
 
         info = self._parse_smil(smil, smil_url, video_id)