'Verify each link in parsed_references and yield the ones that can NOT
be resolved using DNS.'

def _verify_link_domain(self, parsed_references):

    for link in parsed_references:
        domain = link.get_domain()
        if (domain not in self._already_queried):
            self._already_queried.add(domain)
            try:
                socket.gethostbyname(domain)
            except socket.gaierror as se:
                if (se.errno in (socket.EAI_NODATA, socket.EAI_NONAME)):
                    (yield domain)
            except:
                pass
