Use more semantic exit codes so we can detect HTTP errors.

utils/pub/io.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.
 
 /**
  * Helper functionality to make working with IO easier.
  */
 #library('io');
 
 #import('dart:io');
@@ skipping 366 matching lines @@
     }
 
     client.shutdown();
     completer.completeException(e);
   };
 
   connection.onResponse = (response) {
     if (response.statusCode >= 400) {
       client.shutdown();
       completer.completeException(
-          new HttpException(response.statusCode, response.reasonPhrase));
+          new PubHttpException(response.statusCode, response.reasonPhrase));
       return;
     }
 
     completer.complete(response.inputStream);
   };
 
   return completer.future;
 }
 
 /**
@@ skipping 250 matching lines @@
   tarProcess.onExit = completer.complete;
   gzipProcess.onError = completer.completeException;
   gzipProcess.onError = completer.completeException;
 
   return completer.future.transform((exitCode) => exitCode == 0);
 }
 
 /**
  * Exception thrown when an HTTP operation fails.
  */
-class HttpException implements Exception {
+class PubHttpException implements Exception {
   final int statusCode;
   final String reason;
 
-  const HttpException(this.statusCode, this.reason);
+  const PubHttpException(this.statusCode, this.reason);
 }
 
 /**
  * Exception thrown when an operation times out.
  */
 class TimeoutException implements Exception {
   final String message;
 
   const TimeoutException(this.message);
 }
@@ skipping 32 matching lines @@
   return new Directory(entry);
 }
 
 /**
  * Gets a [Uri] for [uri], which can either already be one, or be a [String].
  */
 Uri _getUri(uri) {
   if (uri is Uri) return uri;
   return new Uri.fromString(uri);
 }