Show nicer errors on some server failures.

utils/tests/pub/pub_update_hosted_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('test_pub.dart');
 #import('../../../pkg/unittest/unittest.dart');
 
 main() {
+  test('fails gracefully if the url does not resolve', () {
+    dir(appPath, [
+      pubspec({
+        "name": "myapp",
+        "dependencies": {
+          "foo": {
+            "hosted": {
+              "name": "foo",
+              "url": "http://pub.invalid"
+            }
+          }
+         }
+      })
+    ]).scheduleCreate();
+
+    schedulePub(args: ['update'],
+        error: const RegExp('Could not resolve URL "http://pub.invalid".'));
+
+    run();
+  });
+
+  test('fails gracefully if the package does not exist', () {
+    servePackages([]);
+
+    appDir([dependency("foo", "1.2.3")]).scheduleCreate();
+
+    schedulePub(args: ['update'],
+        error: const RegExp('Could not find package "foo" on '
+                            'http://localhost:'));
+
+    run();
+  });
+
   test("updates one locked pub server package's dependencies if it's "
       "necessary", () {
     servePackages([
       package("foo", "1.0.0", [dependency("foo-dep")]),
       package("foo-dep", "1.0.0")
     ]);
 
     appDir([dependency("foo")]).scheduleCreate();
 
     schedulePub(args: ['install'],
@@ skipping 146 matching lines @@
 
     packagesDir({
       "foo": "1.0.0",
       "bar": null,
       "shared-dep": "2.0.0"
     }).scheduleValidate();
 
     run();
   });
 }