I can see compass support recently have been removed from angular-cli, is there a way to install it ourselves in our project?

What about other sass mixins like sass-flex-mixin? I've tried to install the node module and add the path ../node_modules/sass-flex-mixin/_flex.scss to styles in our angular-cli.json file, but I just get this error:

ERROR in ./src/app/app.component.scss
Module build failed: 
@import "sass-flex-mixin/_flex";
^
      File to import not found or unreadable: sass-flex-mixin/_flex