python3: deprecate __metaclass__ attribute (#31182)

src/authentic2/attributes_ng/sources/__init__.py

@@ -1,11 +1,13 @@
 import abc
 
+from django.utils import six
+
+
+@six.add_metaclass(abc.ABCMeta)
 class BaseAttributeSource(object):
     '''
     Base class for attribute sources
     '''
-    __metaclass__ = abc.ABCMeta
-
     @abc.abstractmethod
     def get_instances(self, ctx):
         pass

src/authentic2/manager/views.py

@@ -54,11 +54,9 @@ class MultipleOUMixin(object):
         return super(MultipleOUMixin, self).get_context_data(**kwargs)
 
 
+@six.add_metaclass(MediaMixinBase)
 class MediaMixin(object):
     '''Expose needed CSS and JS files as a media object'''
-
-    __metaclass__ = MediaMixinBase
-
     class Media:
         js = (
             reverse_lazy('a2-manager-javascript-catalog'),

src/authentic2/passwords.py

@@ -2,12 +2,12 @@ import string
 import random
 import re
 import abc
-import six
 
 from django.utils.translation import ugettext as _
 from django.utils.module_loading import import_string
 from django.utils.functional import lazy
 from django.utils.safestring import mark_safe
+from django.utils import six
 from django.core.exceptions import ValidationError
 
 from . import app_settings
@@ -34,9 +34,8 @@ def generate_password():
     return ''.join(new_password)
 
 
+@six.add_metaclass(abc.ABCMeta)
 class PasswordChecker(object):
-    __metaclass__ = abc.ABCMeta
-
     class Check(object):
         def __init__(self, label, result):
             self.label = label