Roll Observatory packages and add a roll script

packages/quiver/lib/testing/src/equality/equality.dart

 // Copyright 2014 Google Inc. All Rights Reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 195 matching lines @@
 }
 
 class MatchError extends Error {
   final message;
 
   /// The [message] describes the match error.
   MatchError([this.message]);
 
   String toString() => message;
 }