docs: function(err, System) {
        err = String(err);
        // Look for common issues in the error message, and try to add hints to them
        switch (true) {
          // Some people use ".es6" instead of ".js" for ES6 code
        case /^Error loading ".*\.es6" at .*\.es6\.js/.test(err):
          return err + '\nHint: If you use ".es6" as an extension, ' +
            'add this to your SystemJS paths config: {"*.es6": "*.es6"}';
        case /^TypeError: Illegal module name "\/base\//.test(err):
          return err + '\nHint: Is the working directory different when you run karma?' +
            '\nYou may need to change the baseURL of your SystemJS config inside your karma config.' +
            '\nIt\'s currently checking "' + System.baseURL + '"' +
            '\nNote: "/base/" is where karma serves files from.';
        }
  
        return err;
      }