Keystone with Material Design Bootstrap Incompatible units: 'rem' and 'px'

Has anyone been able to add SCSS from Material Design Bootstrap to the default Keystone.js template ?

I'm new to node.js and front-end development, so I'm not sure what I'm doing, but I've added a base folder MDB

to mine public/styles

. After that I changed sites.scss

, I commented @import "site/variables";

and @import "site/layout";

, and I added @import "mdb";

, but it didn't really work. I am getting the error:

in /my_path/public/styles/mdb/free/data/_variables-b4.scss:320:34
Error thrown for request: /styles/site.css
Error: Incompatible units: 'rem' and 'px'.
    at options.error (/my_path/node_modules/node-sass/lib/index.js:291:26)

      

        
        
        
      

    

Any idea?