Add flag to disable capturing stack traces.

utils/tests/pub/update/hosted/unlock_if_necessary_test.dart

 // Copyright (c) 2012, 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.
 
 library pub_tests;
 
 import 'dart:io';
 
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
 
 main() {
+  initConfig();
   integration("updates one locked pub server package's dependencies if it's "
       "necessary", () {
     servePackages([
       packageMap("foo", "1.0.0", [dependencyMap("foo-dep")]),
       packageMap("foo-dep", "1.0.0")
     ]);
 
     d.appDir([dependencyMap("foo")]).create();
 
     schedulePub(args: ['install'],
@@ skipping 11 matching lines @@
 
     schedulePub(args: ['update', 'foo'],
         output: new RegExp(r"Dependencies updated!$"));
 
     d.packagesDir({
       "foo": "2.0.0",
       "foo-dep": "2.0.0"
     }).validate();
   });
 }