[udemy] Stringify video id

youtube_dl/extractor/udemy.py

@@ -5,6 +5,7 @@ import re
 from .common import InfoExtractor
 from ..compat import (
     compat_HTTPError,
+    compat_str,
     compat_urllib_request,
     compat_urlparse,
 )
@@ -207,7 +208,7 @@ class UdemyIE(InfoExtractor):
             if youtube_url:
                 return self.url_result(youtube_url, 'Youtube')
 
-        video_id = asset['id']
+        video_id = compat_str(asset['id'])
         thumbnail = asset.get('thumbnail_url') or asset.get('thumbnailUrl')
         duration = float_or_none(asset.get('data', {}).get('duration'))