this is a hack to have some selective components from bootstrap overriden without copying the whole bootstrap.scss with all its @imports
function(url, prev, done) {
        if (url.indexOf('bootstrap/') === 0) {
          var component = url.substr('bootstrap/'.length+1);
          var file = cmsDir+'/src/scss/bootstrap/_'+component+'.scss';
          try {
            var stats = fs.lstatSync(file);

            if (stats.isFile()) {
              return { file: file };
            }
          } catch (ex) {
            // file does not exist
          }
        }

        return sass.compiler.NULL; // do nothing
      }