docs: def download_file(self, url, filename):
          """ Download file from url to filename. """
          self.print_message("Downloading to file '%s' from URL '%s'" % (filename, url))
          try:
              db_file = urllib2.urlopen(url)
              with open(filename, 'wb') as output:
                  output.write(db_file.read())
              db_file.close()
          except Exception as e:
              self.error(str(e))
          self.print_message("File downloaded")