因为less-loader的版本过高
"devDependencies": { "css-loader": "^4.3.0", "less": "^4.1.1", "less-loader": "^10.0.0", "style-loader": "^1.3.0" }
改为:
"devDependencies": { ... "less-loader": "^6.0.0" }
重新npm install
重启