复制yml文件时图标不是“绿叶”图标，感觉不是真的yml
并且运行结果报错，提示
Whitelabel Error Page
This application has no explicit mapping for /error, so you are seeing this as a fallback.
Mon Apr 23 17:32:50 CST 2018
There was an unexpected error (type=Not Found, status=404).
No message available
求解！谢谢老师！
