Start CLI REPL.

def cmdloop(self):
        """Start CLI REPL."""
        while True:
            cmdline = input(self.prompt)
            tokens = shlex.split(cmdline)
            if not tokens:
                if self.last_cmd:
                    tokens = self.last_cmd
                else:
                    print('No previous command.')
                    continue
            if tokens[0] not in self.commands:
                print('Invalid command')
                continue
            command = self.commands[tokens[0]]
            self.last_cmd = tokens
            try:
                if command(self.state, tokens):
                    break
            except CmdExit:
                continue
            except Exception as e:
                if e not in self.safe_exceptions:
                    logger.exception('Error!')