dans les Manager/QuerySet customisé renvoit une sous-classe du QuerySet customisé dans la méthode none()

polynum/utils.py

@@ -7,6 +7,7 @@ import time
 import django.core.cache
 from django.core.urlresolvers import RegexURLPattern, RegexURLResolver
 from django.db import models
+from django.db.models import query
 
 def get_next_workable_day(today=None, hours=0, days=2, increment_hours=0, increment_days=1):
     if today is None:
@@ -183,6 +184,10 @@ class QuerySetManager(models.Manager):
     def get_query_set(self):
         return self.queryset_class(self.model)
 
+    def none(self):
+        klass = type("_InstrumentedEmptyQuerySet_%s" % self.__class__.__name__, (query.EmptyQuerySet, self.__class__), {}) 
+        return self._clone(klass=klass)
+
     def __getattr__(self, attr, *args):
         try:
             return getattr(self.__class__, attr, *args)
@@ -194,6 +199,10 @@ class QuerySet(models.query.QuerySet):
     """Base QuerySet class for adding custom methods that are made
     available on both the manager and subsequent cloned QuerySets"""
 
+    def none(self):
+        klass = type("_InstrumentedEmptyQuerySet_%s" % self.__class__.__name__, (query.EmptyQuerySet, self.__class__), {}) 
+        return self._clone(klass=klass)
+
     @classmethod
     def as_manager(cls, ManagerClass=QuerySetManager):
         return ManagerClass(cls)