use pure metaclass definition
from django.forms import MediaDefiningClass
from django.forms.fields import ChoiceField
-from django.utils.six import with_metaclass
from django.utils.translation import ugettext_lazy as _
from django.template.loader import get_template, TemplateDoesNotExist
from entangled.forms import EntangledModelFormMixin
@@ -17,7 +16,7 @@ class RenderTemplateFormMixin(EntangledModelFormMixin):
entangled_fields = {'glossary': ['render_template']}
-class RenderTemplateMixin(with_metaclass(MediaDefiningClass)):
+class RenderTemplateMixin(metaclass=MediaDefiningClass):
"""
If a Cascade plugin is listed in ``settings.CMSPLUGIN_CASCADE['plugins_with_extra_render_templates']``,
then this ``RenderTemplateMixin`` class is added automatically to its plugin class in order
