close connection(s) to <host>
        host is the host:port spec, as in 'www.cnn.com:8080' as passed in.
        no error occurs if there is no connection to that host.

def close_connection(self, host):
        """close connection(s) to <host>
        host is the host:port spec, as in 'www.cnn.com:8080' as passed in.
        no error occurs if there is no connection to that host."""
        for h in self._cm.get_all(host):
            self._cm.remove(h)
            h.close()