Remove DirectoryException and LinkException from dart:io and use FileException instaed.

sdk/lib/_internal/pub/lib/src/io.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.
 
 /// Helper functionality to make working with IO easier.
 library pub.io;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
@@ skipping 198 matching lines @@
 /// exist, creates them.
 String ensureDir(String dirPath) {
   log.fine("Ensuring directory $dirPath exists.");
   var dir = new Directory(dirPath);
   if (dirPath == '.' || dirExists(dirPath)) return dirPath;
 
   ensureDir(path.dirname(dirPath));
 
   try {
     createDir(dirPath);
-  } on DirectoryException catch (ex) {
+  } on FileSystemException catch (ex) {
     // Error 17 means the directory already exists (or 183 on Windows).
     if (ex.osError.errorCode == 17 || ex.osError.errorCode == 183) {
       log.fine("Got 'already exists' error when creating directory.");
     } else {
       throw ex;
     }
   }
 
   return dirPath;
 }
@@ skipping 604 matching lines @@
   const PubProcessResult(this.stdout, this.stderr, this.exitCode);
 
   bool get success => exitCode == 0;
 }
 
 /// 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 Uri.parse(uri);
 }