def METHOD_NAME(self, response, url):
    """
    Assert that a response does not contain a link to a given URL.
    The body of the response must not contain the exact string
    '<a href="X"', where X is the HTML-escaped URL.  Other links
    will be ignored.
    """
    link = '<a href="{}"'.format(escape(url))
    self.assertNotIn(link.encode(), response.content)