[py3] Replaced basestring by six.string_types.

tests/regressiontests/staticfiles_tests/tests.py

@@ -20,6 +20,7 @@ from django.test.utils import override_settings
 from django.utils.encoding import smart_unicode
 from django.utils.functional import empty
 from django.utils._os import rmtree_errorhandler
+from django.utils import six
 
 from django.contrib.staticfiles import finders, storage
 
@@ -83,7 +84,7 @@ class BaseStaticFilesTestCase(object):
         self.assertRaises(IOError, self._get_file, filepath)
 
     def render_template(self, template, **kwargs):
-        if isinstance(template, basestring):
+        if isinstance(template, six.string_types):
             template = loader.get_template_from_string(template)
         return template.render(Context(kwargs)).strip()