webpage = self._download_webpage(url, video_id, 'Downloading page')
 
         mobj = re.search(r'(?m)fo\.addVariable\("file",\s"(?P<fileid>[\da-z]+)"\);\n'
-                         '\s+fo\.addVariable\("s",\s"(?P<serverid>\d+)"\);', webpage)
+                         r'\s+fo\.addVariable\("s",\s"(?P<serverid>\d+)"\);', webpage)
         if mobj is None:
             raise ExtractorError('Video %s does not exist' % video_id, expected=True)