Migrate pub away from throwing strings.

utils/pub/command_lish.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 command_lish;
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:json';
 import 'dart:uri';
@@ skipping 72 matching lines @@
         return location;
       }).then((location) => client.get(location))
         .then(handleJsonSuccess);
     }).catchError((error) {
       if (error is! PubHttpException) throw error;
       var url = error.response.request.url;
       if (urisEqual(url, cloudStorageUrl)) {
         // TODO(nweiz): the response may have XML-formatted information about
         // the error. Try to parse that out once we have an easily-accessible
         // XML parser.
-        throw 'Failed to upload the package.';
+        throw new Exception('Failed to upload the package.');
       } else if (urisEqual(Uri.parse(url.origin), Uri.parse(server.origin))) {
         handleJsonError(error.response);
       } else {
         throw error;
       }
     });
   }
 
   Future onRun() {
     if (force && dryRun) {
@@ skipping 94 matching lines @@
       return confirm(message).then((confirmed) {
         if (!confirmed) {
           log.error("Package upload canceled.");
           return false;
         }
         return true;
       });
     });
   }
 }