Use "package:" imports for pub.

test/list_package_dirs/pubspec_error_test.dart

Index: test/list_package_dirs/pubspec_error_test.dart
diff --git a/test/list_package_dirs/pubspec_error_test.dart b/test/list_package_dirs/pubspec_error_test.dart
index 6e4a4ee4b16e6433d4d84fb0e06f0b756e094191..b8855da46b519f01793f523da529463f390a4c98 100644
--- a/test/list_package_dirs/pubspec_error_test.dart
+++ b/test/list_package_dirs/pubspec_error_test.dart
@@ -3,10 +3,10 @@
 // BSD-style license that can be found in the LICENSE d.file.
 
 import 'package:path/path.dart' as path;
+import 'package:pub/src/exit_codes.dart' as exit_codes;
+import 'package:pub/src/io.dart';
 import 'package:scheduled_test/scheduled_test.dart';
 
-import '../../lib/src/exit_codes.dart' as exit_codes;
-import '../../lib/src/io.dart';
 import '../descriptor.dart' as d;
 import '../test_pub.dart';