How to use the fcp.node.FCPNodeFailure function in fcp

node message if pending or failed
            - rawcmd - a raw command buffer to send directly
            - options specific to command such as 'URI'
            - timeout - timeout in seconds for job completion, default 1 year
            - waituntilsent - whether to block until this command has been sent
              to the node, default False
            - keep - whether to keep the job on our jobs list after it completes,
              default False
        
        Returns:
            - if command is sent in sync mode, returns the result
            - if command is sent in async mode, returns a JobTicket
              object which the client can poll or block on later
        """
        if not self.nodeIsAlive:
            raise FCPNodeFailure("%s:%s: node closed connection" % (cmd, id))
    
        log = self._log
    
        log(DEBUG, "_submitCmd: kw=%s" % kw)
    
        async = kw.pop('async', False)
        stream = kw.pop('stream', None)
        waituntilsent = kw.pop('waituntilsent', False)
        keepjob = kw.pop('keep', False)
        timeout = kw.pop('timeout', ONE_YEAR)
        job = JobTicket(
            self, id, cmd, kw,
            verbosity=self.verbosity, logger=self._log, keep=keepjob,
            stream=stream)
    
        log(DEBUG, "_submitCmd: timeout=%s" % timeout)

def read(n):
            if n > 1:
                log(DEBUG, "read: want %d bytes" % n)
            chunks = []
            remaining = n
            while remaining > 0:
                chunk = self.socket.recv(remaining)
                chunklen = len(chunk)
                if chunk:
                    chunks.append(chunk)
                else:
                    self.nodeIsAlive = False
                    raise FCPNodeFailure("FCP socket closed by node")
                remaining -= chunklen
                if remaining > 0:
                    if n > 1:
                        log(DEBUG,
                            "wanted %s, got %s still need %s bytes" % (n, chunklen, remaining)
                            )
                    pass
            buf = "".join(chunks)
            return buf