Use "package:" imports for pub.

test/barback/utils.dart

 // Copyright (c) 2014, 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.
 
+import 'package:pub/src/exit_codes.dart' as exit_codes;
 import 'package:scheduled_test/scheduled_test.dart';
 
-import '../../lib/src/exit_codes.dart' as exit_codes;
 import '../test_pub.dart';
 
 /// Runs separate integration tests for "pub build", "pub serve", and
 /// "pub build --format json" and validates that in all cases, it fails with
 /// an expected error message and exits with [exitCode].
 ///
 /// The integrations assume set up is already done, so you will likely want to
 /// call [setUp] before this.
 ///
 /// If [error] is provided, then both pub build and pub serve should exit with
@@ skipping 33 matching lines @@
         },
         exitCode: exitCode);
   });
 
   integration("serve fails $description", () {
     schedulePub(args: ["serve"]..addAll(args),
         error: serveExpectation,
         exitCode: exitCode);
   });
 }