Fix analyzer hints and warnings in test/.

test/global/run/implicit_executable_name_test.dart

Index: test/global/run/implicit_executable_name_test.dart
diff --git a/test/global/run/implicit_executable_name_test.dart b/test/global/run/implicit_executable_name_test.dart
index 6da88a2a111fcb54c27438c36417ffd04a2e7f47..b4f1584b7ffc4ca560c7f0536b110a39f0f69afb 100644
--- a/test/global/run/implicit_executable_name_test.dart
+++ b/test/global/run/implicit_executable_name_test.dart
@@ -2,8 +2,6 @@
 // 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 '../../descriptor.dart' as d;
 import '../../test_pub.dart';