Get rid of all the library tags.

test/transformer/prints_a_transform_interface_error_test.dart

 // Copyright (c) 2013, 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 '../descriptor.dart' as d;
 import '../test_pub.dart';
 import '../serve/utils.dart';
 
 final transformer = """
 import 'dart:async';
 
 import 'package:barback/barback.dart';
 
 class RewriteTransformer extends Transformer {
@@ skipping 23 matching lines @@
 
     pubGet();
     var server = pubServe();
     server.stderr.expect(emitsLines(
         "Build error:\n"
         "Transform Rewrite on myapp|web/foo.txt threw error: Class "
             "'RewriteTransformer' has no instance method 'apply'."));
     endPubServe();
   });
 }