Get rid of all the library tags.

test/transformer/asset_not_found_exceptions_are_detectable_test.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS d.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:convert';
 
 import 'package:scheduled_test/scheduled_stream.dart';
 
 import '../descriptor.dart' as d;
 import '../test_pub.dart';
 import '../serve/utils.dart';
 
 final transformer = """
 import 'dart:async';
@@ skipping 44 matching lines @@
       "package": "myapp",
       "path": "nonexistent"
     }));
     endPubServe();
 
     // Since the AssetNotFoundException was caught and handled, the server
     // shouldn't print any error information for it.
     server.stderr.expect(isDone);
   });
 }