Stop working around issue 7781 in Pub.

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:async';
 import 'dart:io';
 import 'dart:isolate';
@@ skipping 171 matching lines @@
   if (path == '.') return new Future.immediate(new Directory('.'));
 
   return dirExists(path).then((exists) {
     if (exists) {
       log.fine("Directory $path already exists.");
       return new Future.immediate(new Directory(path));
     }
 
     return ensureDir(dirname(path)).then((_) {
       return createDir(path).catchError((asyncError) {
-        var error = getRealError(asyncError);
-        if (error is! DirectoryIOException) throw asyncError;
+        if (asyncError.error is! DirectoryIOException) throw asyncError;
         // Error 17 means the directory already exists (or 183 on Windows).
-        if (error.osError.errorCode == 17 || error.osError.errorCode == 183) {
+        if (asyncError.error.osError.errorCode == 17 ||
+            asyncError.error.osError.errorCode == 183) {
           log.fine("Got 'already exists' error when creating directory.");
           return _getDirectory(path);
         }
 
         throw asyncError;
       });
     });
   });
 }
 
@@ skipping 822 matching lines @@
 Directory _getDirectory(entry) {
   if (entry is Directory) return entry;
   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);
 }