Use "package:" imports for pub.

test/run/errors_if_only_transitive_dependency_test.dart

Index: test/run/errors_if_only_transitive_dependency_test.dart
diff --git a/test/run/errors_if_only_transitive_dependency_test.dart b/test/run/errors_if_only_transitive_dependency_test.dart
index c644b53114d8400f83989223cbcd674077654a35..7c8f04899526dc1b9372746e6e361a16de33d04c 100644
--- a/test/run/errors_if_only_transitive_dependency_test.dart
+++ b/test/run/errors_if_only_transitive_dependency_test.dart
@@ -2,7 +2,8 @@
 // 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';