Run dartfmt on remaining unformated pkg packages

pkg/testing/lib/src/error_handling.dart

 // Copyright (c) 2016, 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.md file.
 
 library testing.error_handling;
 
-import 'dart:async' show
-    Future;
+import 'dart:async' show Future;
 
-import 'dart:io' show
-    exitCode,
-    stderr;
+import 'dart:io' show exitCode, stderr;
 
-import 'dart:isolate' show
-    ReceivePort;
+import 'dart:isolate' show ReceivePort;
 
 Future withErrorHandling(Future f()) async {
   final ReceivePort port = new ReceivePort();
   try {
     return await f();
   } catch (e, trace) {
     exitCode = 1;
     stderr.writeln(e);
     if (trace != null) {
       stderr.writeln(trace);
     }
   } finally {
     port.close();
   }
 }