Remove use of deprecated test functions.

utils/tests/pub/pubspec_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('pubspec_test');
 
 #import('../../../lib/unittest/unittest.dart');
 #import('../../pub/pubspec.dart');
 #import('../../pub/source.dart');
 #import('../../pub/source_registry.dart');
@@ skipping 54 matching lines @@
 # See http://www.dartlang.org/docs/pub-package-manager/ for details
 ''', sources);
         expect(pubspec.version, equals(Version.none));
         expect(pubspec.dependencies, isEmpty);
       });
     });
   });
 }
 
 throwsBadFormat(function) {
-  expectThrow(function, (e) => e is FormatException);
+  expect(function, throwsA((e) => e is FormatException));
 }