          with self.assertRaises(IOError):
              self._get_file(filepath)
  
      def render_template(self, template, **kwargs):
          if isinstance(template, six.string_types):
              template = Template(template)
          return template.render(Context(**kwargs)).strip()
  
      def static_template_snippet(self, path, asvar=False):
          if asvar:
 
</s> remove         if isinstance(value, six.string_types):
 </s> add         if isinstance(value, str): </s> remove         if default_unit and isinstance(default_unit, six.string_types):
 </s> add         if default_unit and isinstance(default_unit, str): </s> remove         if not isinstance(string_if_invalid, six.string_types):
 </s> add         if not isinstance(string_if_invalid, str): </s> remove         return six.text_type(self.biggie)
 </s> add         return str(self.biggie) </s> remove         if isinstance(self.remote_field.through, six.string_types) or not self.remote_field.through._meta.managed:
 </s> add         if isinstance(self.remote_field.through, str) or not self.remote_field.through._meta.managed:
        if isinstance(template, str):
          with self.assertRaises(IOError):
              self._get_file(filepath)
  
      def render_template(self, template, **kwargs):
        if isinstance(template, str):
              template = Template(template)
          return template.render(Context(**kwargs)).strip()
  
      def static_template_snippet(self, path, asvar=False):
          if asvar:
keep keep keep keep replace keep keep keep keep keep
 Refs #23919 -- Removed six.<various>_types usage

Thanks Tim Graham and Simon Charette for the reviews. 
tests/staticfiles_tests/cases.py