code: def _DownloadUrl(self, url, dest_dir):
      
      dest_file = tempfile.NamedTemporaryFile(dir=dest_dir, delete=False)
      dest_file.close()
      dest = dest_file.name
  
      self.logger.info('Downloading url from %s to %s.', url, dest)
      try:
        urlretrieve.urlretrieve(url, dest)
        return dest
      except (httpclient.HTTPException, socket.error, urlerror.URLError) as e:
        self.logger.warning('Could not download %s. %s.', url, str(e))
      except Exception as e:
        self.logger.warning('Exception downloading %s. %s.', url, str(e))
      return None
docs: Download a script from a given URL.
  
      Args:
        url: string, the URL to download.
        dest_dir: string, the path to a directory for storing metadata scripts.
  
      Returns:
        string, the path to the file storing the metadata script.