cmd handler for downloading firmware

def cmd_fw_download(self, args):
        '''cmd handler for downloading firmware'''
        stuff = self.filtered_rows_from_args(args)
        if stuff is None:
            return
        (filtered, remainder) = stuff
        if len(filtered) == 0:
            print("fw: No firmware specified")
            return
        if len(filtered) > 1:
            print("fw: No single firmware specified")
            return

        firmware = filtered[0]["_firmware"]
        url = firmware["url"]

        try:
            print("fw: URL: %s"  % (url,))
            filename=os.path.basename(url)
            files = []
            files.append((url,filename))
            child = multiproc.Process(target=mp_util.download_files, args=(files,))
            child.start()
        except Exception as e:
            print("fw: download failed")
            print(e)