Make source map location information more readable.

pkg/csslib/test/selector_test.dart

 // Copyright (c) 2012, 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 selector_test;
 
 import 'package:unittest/unittest.dart';
 import 'testing.dart';
 import 'package:csslib/parser.dart';
 
@@ skipping 36 matching lines @@
 }
 
 // TODO(terry): Move this failure case to a failure_test.dart when the analyzer
 //              and validator exit then they'll be a bunch more checks.
 void testSelectorFailures() {
   var errors = [];
 
   // Test for invalid class name (can't start with number).
   var selectorAst = selector('.foobar .1a-story .xyzzy', errors: errors);
   expect(errors.isEmpty, false);
-  expect(errors[0].toString(), r'''
-error :1:9: name must start with a alpha character, but found a number
-.foobar .1a-story .xyzzy
-        ^^''');
+  expect(errors[0].toString(),
+      'error on line 1, column 9: name must start with a alpha character, but '
+        'found a number\n'
+      '.foobar .1a-story .xyzzy\n'
+      '        ^^');
 }
 
 main() {
   test('Valid Selectors', testSelectorSuccesses);
   test('Invalid Selectors', testSelectorFailures);
 }