anchor.diff:        '--splits',
         '$newVersion=1',
       ];
  -    if (migrateTraffic) {
  -      args.add('--migrate');
  -    }
       args.add('-q');
  -    final pr = await _runGCloudApp(args);
  -    if (pr.exitCode != 0) {
  -      print('[ERR] Couldn\'t migrate traffic for $service.');
  -      print(pr.stderr);
  -      exit(1);
  -    }
  +    await _runGCloudApp(args, 'Couldn\'t migrate traffic for $service.');
     }
   
     Future _deleteOldVersion() async {
       if (_oldVersion == null) return;
  -    final pr = await _runGCloudApp(
  -        ['versions', 'delete', '--service', service, _oldVersion, '-q']);
  +    await _runGCloudApp(
  +        ['versions', 'delete', '--service', service, _oldVersion, '-q'],
  +        'Couldn\'t delete old version of $service.');
  +  }
  +
  +  Future<ProcessResult> _runGCloudApp(
  +      List<String> args, String errorMessage) async {
  +    final allArgs = [
  +      '--project',
  +      project,
  +      'app',
  +    ]..addAll(args);
  +
  +    final pr = await Process.run('gcloud', allArgs);
       if (pr.exitCode != 0) {
  -      print('[ERR] Couldn\'t delete old version of $service.');
  -      print(pr.stderr);
  +      print('[ERR] $errorMessage');
  +      print('Due to executing "gcloud ${allArgs.join(' ')}":');
  +      print('stdout:\n    ${pr.stdout.replaceAll('\n', '    \n')}');
  +      print('stderr:\n    ${pr.stderr.replaceAll('\n', '    \n')}');
         exit(1);
       }
  +    return pr;
     }
  -
  -  Future<ProcessResult> _runGCloudApp(List<String> args) => Process.run(
  -      'gcloud',
  -      [
  -        '--project',
  -        project,
  -        'app',
  -      ]..addAll(args));
   }
  
positive.code: 
    Future _gcloudDeploy() async {
      final String yamlFile = service == 'default' ? 'app.yaml' : '$service.yaml';
      final pr = await _runGCloudApp(
        ['deploy', yamlFile, '--no-promote', '-v', newVersion, '-q'],
      );
      if (pr.exitCode != 0) {
        print('[ERR] Couldn\'t deploy $service.');
        print(pr.stderr);
        exit(1);
      }
    }
  
    String get baseUrl {
  
negative.code: 
    Future _detectOldVersion() async {
      final pr = await _runGCloudApp(
          ['versions', 'list', '--service', service, '--format=value(id)'],
          'Couldn\'t detect old $service version.');
  
      _oldVersion = pr.stdout.trim();
      if (_oldVersion.contains('\n')) {
        print('[WARN] Multiple existing versions detected: '
  