vue提示The project seems to require yarn but it's not installed？

Question

创建项目后，直接运行yarn serve 提示
Error: The project seems to require yarn but it's not installed.
只有删了yarn.local文件才能继续运行，但下一次yarn add之后要再次删除。
不然不能运行。
运行就提示，而且直接中断。

运行：npm install yarn -g后直接运行yarn serve
依然报错