Update unittest to new package layout.

utils/tests/pub/pub_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');
+#import('../../../pkg/unittest/lib/unittest.dart');
 
 final USAGE_STRING = """
     Pub is a package manager for Dart.
 
     Usage: pub command [arguments]
 
     Global options:
     -h, --help          Prints this usage information
         --version       Prints the version of Pub
         --[no-]trace    Prints a stack trace when an error occurs
@@ skipping 32 matching lines @@
           Unknown command "quylthulg".
           Run "pub help" to see available commands.
           ''',
           exitCode: 64);
     });
   });
 
   test('displays the current version', () =>
     runPub(args: ['version'], output: VERSION_STRING));
 }