Use "package:" imports for pub.

test/run/errors_if_only_transitive_dependency_test.dart

 // Copyright (c) 2014, 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.
 
-import '../../lib/src/exit_codes.dart' as exit_codes;
+import 'package:pub/src/exit_codes.dart' as exit_codes;
+
 import '../descriptor.dart' as d;
 import '../test_pub.dart';
 
 main() {
   initConfig();
   integration('Errors if the script is in a non-immediate dependency.', () {
     d.dir("foo", [
       d.libPubspec("foo", "1.0.0"),
       d.dir("bin", [
         d.file("bar.dart", "main() => print('foobar');")
@@ skipping 13 matching lines @@
     ]).create();
 
     pubGet();
 
     var pub = pubRun(args: ["foo:script"]);
     pub.stderr.expect('Package "foo" is not an immediate dependency.');
     pub.stderr.expect('Cannot run executables in transitive dependencies.');
     pub.shouldExit(exit_codes.DATA);
   });
 }