问题：npm WARN ajv-keywords@3.2.0 requires a peer of ajv@^6.0.0 but none is installed.

在react项目中， npm install 时，报错：

npm WARN ajv-keywords@3.2.0 requires a peer of ajv@^6.0.0 but none is installed. 

报错解决方案：

命令：npm install ajv@^6.0.0