[slideshare] Fix description extraction and modernize

The ‘og:description’  property doesn’t contain the full description

youtube_dl/extractor/slideshare.py

@@ -1,3 +1,5 @@
+from __future__ import unicode_literals
+
 import re
 import json
 
@@ -12,11 +14,12 @@ class SlideshareIE(InfoExtractor):
     _VALID_URL = r'https?://www\.slideshare\.net/[^/]+?/(?P<title>.+?)($|\?)'
 
     _TEST = {
-        u'url': u'http://www.slideshare.net/Dataversity/keynote-presentation-managing-scale-and-complexity',
-        u'file': u'25665706.mp4',
-        u'info_dict': {
-            u'title': u'Managing Scale and Complexity',
-            u'description': u'This was a keynote presentation at the NoSQL Now! 2013 Conference & Expo (http://www.nosqlnow.com). This presentation was given by Adrian Cockcroft from Netflix',
+        'url': 'http://www.slideshare.net/Dataversity/keynote-presentation-managing-scale-and-complexity',
+        'info_dict': {
+            'id': '25665706',
+            'ext': 'mp4',
+            'title': 'Managing Scale and Complexity',
+            'description': 'This was a keynote presentation at the NoSQL Now! 2013 Conference & Expo (http://www.nosqlnow.com). This presentation was given by Adrian Cockcroft from Netflix.',
         },
     }
 
@@ -26,15 +29,17 @@ class SlideshareIE(InfoExtractor):
         webpage = self._download_webpage(url, page_title)
         slideshare_obj = self._search_regex(
             r'var slideshare_object =  ({.*?}); var user_info =',
-            webpage, u'slideshare object')
+            webpage, 'slideshare object')
         info = json.loads(slideshare_obj)
-        if info['slideshow']['type'] != u'video':
-            raise ExtractorError(u'Webpage type is "%s": only video extraction is supported for Slideshare' % info['slideshow']['type'], expected=True)
+        if info['slideshow']['type'] != 'video':
+            raise ExtractorError('Webpage type is "%s": only video extraction is supported for Slideshare' % info['slideshow']['type'], expected=True)
 
         doc = info['doc']
         bucket = info['jsplayer']['video_bucket']
         ext = info['jsplayer']['video_extension']
         video_url = compat_urlparse.urljoin(bucket, doc + '-SD.' + ext)
+        description = self._html_search_regex(
+            r'<p class="description.*?"[^>]*>(.*?)</p>', webpage, 'description')
 
         return {
             '_type': 'video',
@@ -43,5 +48,5 @@ class SlideshareIE(InfoExtractor):
             'ext': ext,
             'url': video_url,
             'thumbnail': info['slideshow']['pin_image_url'],
-            'description': self._og_search_description(webpage),
+            'description': description,
         }