报错信息：

  1. ERROR  Failed to compile with 1 errors                                                                                                                   
  3. error  in ./src/styles/element-variables.scss
  5. Module build failed (from ./node_modules/sass-loader/dist/cjs.js):
  6. SassError: Invalid CSS after "...-flex: 0 0 math": expected expression (e.g. 1px, bold), was ".div(1, 5) * 100% !"
  7.         on line 490 of node_modules/element-ui/packages/theme-chalk/src/common/var.scss
  8.         from line 1 of node_modules/element-ui/packages/theme-chalk/src/common/transition.scss
  9.         from line 1 of node_modules/element-ui/packages/theme-chalk/src/base.scss
  10.         from line 1 of node_modules/element-ui/packages/theme-chalk/src/index.scss
  11.         from line 25 of C:\develop\workspace\suokelian-admin-ui\src\styles\element-variables.scss
  12. >> $--group-option-flex: 0 0 math.div(1, 5) * 100% !default;
  14.    ------------------------------^

报错原因：

element-ui 2.15.7版本将node-sass替换为dart-sass。