Support the latest version of the test package.

lib/src/utils.dart

-// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-library metatest.utils;
-
-/// Prepends each line in [text] with [prefix]. If [firstPrefix] is passed, the
-/// first line is prefixed with that instead.
-String prefixLines(String text, {String prefix: '| ', String firstPrefix}) {
-  var lines = text.split('\n');
-  if (firstPrefix == null) {
-    return lines.map((line) => '$prefix$line').join('\n');
-  }
-
-  var firstLine = "$firstPrefix${lines.first}";
-  lines = lines.skip(1).map((line) => '$prefix$line').toList();
-  lines.insert(0, firstLine);
-  return lines.join('\n');
-}