Remove AsyncError with Expando.

tests/standalone/io/https_server_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.
 
 import "package:expect/expect.dart";
 import "dart:io";
 import "dart:uri";
 import "dart:isolate";
 
 const SERVER_ADDRESS = "127.0.0.1";
@@ skipping 25 matching lines @@
             response.listen(
               (_) { },
               onDone: () {
                 client.close();
                 clientPort.close();
                 server.close();
                 Expect.throws(() => server.port);
                 onDone();
               });
         })
-        .catchError((error) {
-          Expect.fail("Unexpected error in Https client: $error");
+        .catchError((e) {
+          String msg = "Unexpected error in Https client: $e";
+          var trace = getAttachedStackTrace(e);
+          if (trace != null) msg += "\nStackTrace: $trace";
+          Expect.fail(msg);
         });
     });
   }
 
   // Test two servers in succession.
   test(() {
     test(() { });
   });
 }
 
 void InitializeSSL() {
   var testPkcertDatabase =
       new Path(new Options().script).directoryPath.append('pkcert/');
   SecureSocket.initialize(database: testPkcertDatabase.toNativePath(),
                           password: 'dartdart');
 }
 
 void main() {
   InitializeSSL();
   testListenOn();
 }