Fix a warning in themes.py

chrome/test/functional/themes.py

 #!/usr/bin/python
 # Copyright (c) 2010 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import glob
 import logging
 import os
 
 import pyauto_functional  # Must be imported before pyauto
@@ skipping 85 matching lines @@
 
     This does not get run automatically. To run:
     python themes.py themes.ThemesTest.Runner
 
     Note: this test requires that a directory of crx files called 'themes'
     exists in the data directory.
     """
     themes_dir = os.path.join(self.DataDir(), 'themes')
     urls_file = os.path.join(self.DataDir(), 'urls.txt')
 
-    assert(os.path.exists(themes_dir),
-           'The dir "%s" must exist' % os.path.abspath(themes_dir))
+    assert os.path.exists(themes_dir), \
+           'The dir "%s" must exist' % os.path.abspath(themes_dir)
 
     group_size = 20
     num_urls_to_visit = 100
 
     urls = [l.rstrip() for l in
             open(urls_file).readlines()[:num_urls_to_visit]]
     failed_themes = glob.glob(os.path.join(themes_dir, '*.crx'))
 
     while failed_themes and group_size:
       failed_themes = self._ReturnCrashingThemes(failed_themes, group_size,
                                                  urls)
       group_size = group_size // 2
 
     self.assertFalse(failed_themes,
                      'Theme(s) in failing group: %s' % failed_themes)
 
 
 if __name__ == '__main__':
   pyauto_functional.Main()