Get rid of all the library tags.

lib/src/exception.dart

 // Copyright (c) 2014, 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.
 
-library http.exception;
-
 /// An exception caused by an error in a pkg/http client.
 class ClientException implements Exception {
   final String message;
 
   /// The URL of the HTTP request or response that failed.
   final Uri uri;
 
   ClientException(this.message, [this.uri]);
 
   String toString() => message;
 }