Use Bot in compare_failures

tools/gardening/lib/src/client.dart

 // Copyright (c) 2017, 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.
 
 import 'dart:async' hide TimeoutException;
 import 'dart:io' hide HttpException;
 
 import 'buildbot_data.dart';
 import 'buildbot_loading.dart';
 import 'buildbot_structures.dart';
@@ skipping 17 matching lines @@
 
   @override
   Future<BuildResult> readResult(BuildUri buildUri) async {
     Duration timeout;
     if (buildUri.buildNumber < 0) {
       timeout = new Duration(seconds: 1);
     }
 
     void skipToPreviousBuildNumber() {
       BuildUri prevBuildUri = buildUri.prev();
-      log('Skip build number '
-          '${buildUri.buildNumber} -> ${prevBuildUri.buildNumber}');
+      log('Skip build number on ${buildUri} -> ${prevBuildUri.buildNumber}');
       buildUri = buildUri.prev();
     }
 
     while (true) {
       try {
         return await readBuildResultFromHttp(_client, buildUri, timeout);
       } on TimeoutException {
         if (timeout != null) {
           skipToPreviousBuildNumber();
           continue;
@@ skipping 63 matching lines @@
         buildUri = buildUri.withBuildNumber(buildNumber);
       }
     }
   }
 
   @override
   void close() {
     // Nothing to do.
   }
 }