Get codebase ready for actually supporting versioning.

utils/pub/utils.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.
 
 /**
  * Generic utility functions. Stuff that should possibly be in core.
  */
 #library('pub_utils');
 
+/** Thrown by methods that parse text when the text isn't a valid. */
+class FormatException implements Exception {
+  final String message;
+
+  FormatException(this.message);
+
+  String toString() => message;
+}
+
 // TODO(rnystrom): Move into String?
 /** Pads [source] to [length] by adding spaces at the end. */
 String padRight(String source, int length) {
   final result = new StringBuffer();
   result.add(source);
 
   while (result.length < length) {
     result.add(' ');
   }
 
@@ skipping 34 matching lines @@
 /**
  * Asserts that [iter] contains only one element, and returns it.
  */
 only(Iterable iter) {
   var iterator = iter.iterator();
   assert(iterator.hasNext());
   var obj = iterator.next();
   assert(!iterator.hasNext());
   return obj;
 }