Improve the error message for pub install without a name key in the pubspec.

utils/tests/pub/pub_update_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('pub_tests');
 
 #import('dart:io');
 
 #import('test_pub.dart');
 #import('../../../pkg/unittest/unittest.dart');
 
 main() {
   group('requires', () {
     test('a pubspec', () {
       dir(appPath, []).scheduleCreate();
 
       schedulePub(args: ['update'],
           error: const RegExp(@'^Could not find a file named "pubspec.yaml"'));
 
       run();
     });
 
     test('a pubspec with a "name" key', () {
       dir(appPath, [
         pubspec({"dependencies": {"foo": null}})
       ]).scheduleCreate();
 
       schedulePub(args: ['update'],
-          error: const RegExp(@'^"pubspec.yaml" must contain a "name" key\.'));
+          error: const RegExp(@'^"pubspec.yaml" is missing the required "name" '
+              @'field \(e\.g\. "name: myapp"\)\.'));
 
       run();
     });
   });
 
   test('creates a self-referential symlink', () {
     // The symlink should use the name in the pubspec, not the name of the
     // directory.
     dir(appPath, [
       pubspec({"name": "myapp_name"})
     ]).scheduleCreate();
 
     schedulePub(args: ['update'],
         output: const RegExp(@"Dependencies updated!$"));
 
     dir(packagesPath, [
       dir("myapp_name", [pubspec({"name": "myapp_name"})])
     ]).scheduleValidate();
 
     run();
   });
 }