YoutubeIE: Fix vevo explicit videos (closes #956)

When an age restricted video is detected it simulates accessing the video from www.youtube.com/v/{video_id}

youtube_dl/extractor/youtube.py

@@ -117,7 +117,19 @@ class YoutubeIE(InfoExtractor):
                 u"uploader": u"IconaPop",
                 u"uploader_id": u"IconaPop"
             }
+        },
+        {
+            u"url":  u"https://www.youtube.com/watch?v=07FYdnEawAQ",
+            u"file":  u"07FYdnEawAQ.mp4",
+            u"note": u"Test VEVO video with age protection (#956)",
+            u"info_dict": {
+                u"upload_date": u"20130703",
+                u"title": u"Justin Timberlake - Tunnel Vision (Explicit)",
+                u"description": u"md5:64249768eec3bc4276236606ea996373",
+                u"uploader": u"justintimberlakeVEVO",
+                u"uploader_id": u"justintimberlakeVEVO"
             }
+        },
     ]
 
 
@@ -410,6 +422,26 @@ def _real_extract(self, url):
 
         # Get video info
         self.report_video_info_webpage_download(video_id)
+        if re.search(r'player-age-gate-content">', video_webpage) is not None:
+            self.report_age_confirmation()
+            age_gate = True
+            # We simulate the access to the video from www.youtube.com/v/{video_id}
+            # this can be viewed without login into Youtube
+            data = compat_urllib_parse.urlencode({'video_id': video_id,
+                                                  'el': 'embedded',
+                                                  'gl': 'US',
+                                                  'hl': 'en',
+                                                  'eurl': 'https://youtube.googleapis.com/v/' + video_id,
+                                                  'asv': 3,
+                                                  'sts':'1588',
+                                                  })
+            video_info_url = 'https://www.youtube.com/get_video_info?' + data
+            video_info_webpage = self._download_webpage(video_info_url, video_id,
+                                    note=False,
+                                    errnote='unable to download video info webpage')
+            video_info = compat_parse_qs(video_info_webpage)
+        else:
+            age_gate = False
             for el_type in ['&el=embedded', '&el=detailpage', '&el=vevo', '']:
                 video_info_url = ('https://www.youtube.com/get_video_info?&video_id=%s%s&ps=default&eurl=&gl=US&hl=en'
                         % (video_id, el_type))
@@ -545,9 +577,15 @@ def _real_extract(self, url):
                     elif 's' in url_data:
                         if self._downloader.params.get('verbose'):
                             s = url_data['s'][0]
-                            player = self._search_regex(r'html5player-(.+?)\.js', video_webpage,
+                            if age_gate:
+                                player_version = self._search_regex(r'ad3-(.+?)\.swf',
+                                    video_info['ad3_module'][0], 'flash player',
+                                    fatal=False)
+                                player = 'flash player %s' % player_version
+                            else:
+                                player = u'html5 player %s' % self._search_regex(r'html5player-(.+?)\.js', video_webpage,
                                     'html5 player', fatal=False)
-                            self.to_screen('encrypted signature length %d (%d.%d), itag %s, html5 player %s' %
+                            self.to_screen('encrypted signature length %d (%d.%d), itag %s, %s' %
                                 (len(s), len(s.split('.')[0]), len(s.split('.')[1]), url_data['itag'][0], player))
                         signature = self._decrypt_signature(url_data['s'][0])
                         url += '&signature=' + signature