misc: restore usage of CallableTrue (#41391)

This reverts commit ca5168f203, as it is
still required by djangorestframework 3.4 used in stretch.

hobo/rest_authentication.py

@@ -8,6 +8,10 @@ from django.contrib.auth import get_user_model
 from django.conf import settings
 from django.contrib.auth.models import AnonymousUser
 from django.db.models.fields import FieldDoesNotExist
+try:
+    from django.utils.deprecation import CallableTrue
+except ImportError:
+    CallableTrue = True
 from django.utils.module_loading import import_string
 
 try:
@@ -18,8 +22,14 @@ except ImportError:
 
 class AnonymousAuthenticServiceUser(AnonymousUser):
     '''This virtual user hold permissions for other publik services'''
-    is_anonymous = True
-    is_authenticated = True
+
+    @property
+    def is_anonymous(self):
+        return CallableTrue
+
+    @property
+    def is_authenticated(self):
+        return CallableTrue
 
     def has_perm(self, perm_or_perms, obj=None):
         return True
@@ -41,8 +51,14 @@ class AnonymousAuthenticServiceUser(AnonymousUser):
 class AnonymousAdminServiceUser(AnonymousUser):
     '''This virtual user hold permissions for other publik services'''
     is_staff = True
-    is_anonymous = True
-    is_authenticated = True
+
+    @property
+    def is_anonymous(self):
+        return CallableTrue
+
+    @property
+    def is_authenticated(self):
+        return CallableTrue
 
     def __unicode__(self):
         return 'Publik Service Admin'