'Abort a file transfer.  Uses out-of-band data.
This does not follow the procedure from the RFC to send Telnet
IP and Synch; that doesn\'t seem to work with the servers I\'ve
tried.  Instead, just send the ABOR command as OOB data.'

def abort(self):

    line = ('ABOR' + CRLF)
    if (self.debugging > 1):
        print '*put    urgent*', self.sanitize(line)
    self.sock.sendall(line, MSG_OOB)
    resp = self.getmultiline()
    if (resp[:3] not in ('426', '225', '226')):
        raise error_proto, resp
