Fix a warning in themes.py

Fix for:
themes.py:106: SyntaxWarning: assertion is always true, perhaps remove
parentheses?

Review URL: http://codereview.chromium.org/6309009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@72016 0039d316-1c4b-4281-b951-d872f2087c98

chrome/test/functional/themes.py

@@ -103,8 +103,8 @@ class ThemesTest(pyauto.PyUITest):
     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