react-native Error watching file

在运行react-native start 出现一下错误

 ERROR  Error watching file for changes: EMFILE
{"code":"EMFILE","errno":"EMFILE","syscall":"Error watching file for changes:","filename":null}
Error: Error watching file for changes: EMFILE
    at exports._errnoException (util.js:1022:11)
    at FSEvent.FSWatcher._handle.onchange (fs.js:1360:11)

有可能是没有安装watchman, 或者更新mac OS后没有更新watchman
执行一下以下命令安装watchman即可
brew install watchman