docs: function errorDiff(err, type, escape) {
    return diff['diff' + type](err.actual, err.expected).map(function(str){
      if (escape) {
        str.value = str.value
          .replace(/\t/g, '<tab>')
          .replace(/\r/g, '<CR>')
          .replace(/\n/g, '<LF>\n');
      }
      if (str.added) return colorLines('diff added', str.value);
      if (str.removed) return colorLines('diff removed', str.value);
      return str.value;
    }).join('');
  }