message: use template strings instead of concatenations
diff: @@ -456,22 +456,14 @@ export /* exported for testing */ function getExtraOptions(
  }
  if (!Array.isArray(options)) {
  const msg =
  - 'The extra options for `' +
  - pathInfo.join('.') +
  - '` (`' +
  - JSON.stringify(options) +
  - '`) are not in an array.';
  + `The extra options for '${pathInfo.join('.')}' ('${JSON.stringify(options)}') are not in an array.`;
  throw new Error(msg);
  }
  return options.map(o => {
  const t = typeof o;
  if (t !== 'string' && t !== 'number' && t !== 'boolean') {
  const msg =
  - 'The extra option for `' +
  - pathInfo.join('.') +
  - '` (`' +
  - JSON.stringify(o) +
  - '`) is not a primitive value.';
  + `The extra option for '${pathInfo.join('.')}' ('${JSON.stringify(o)}') is not a primitive value.`;
  throw new Error(msg);
  }
  return o + '';
  