Don't use external servers in the tests

tests/standalone/io/http_client_exception_test.dart

+// Copyright (c) 2013, 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 "dart:io";
+import "dart:isolate";
+import "dart:uri";
+
+void testInvalidUrl() {
+  HttpClient client = new HttpClient();
+  Expect.throws(
+      () => client.getUrl(Uri.parse('ftp://www.google.com')));
+}
+
+void testBadHostName() {
+  HttpClient client = new HttpClient();
+  ReceivePort port = new ReceivePort();
+  client.get("some.bad.host.name.7654321", 0, "/")
+    .then((request) {
+      Expect.fail("Should not open a request on bad hostname");
+    }).catchError((error) {
+      port.close();  // We expect onError to be called, due to bad host name.
+    }, test: (error) => error is! String);
+}
+
+void main() {
+  testInvalidUrl();
+  testBadHostName();
+}