Using AppPickler is discouraged (use __reduce_keys__)

celery/app/base.py

@@ -66,6 +66,7 @@ def _unpickle_appattr(reverse_name, args):
 
 
 class Celery(object):
+    #: This is deprecated, use :meth:`reduce_keys` instead
     Pickler = AppPickler
 
     SYSTEM = platforms.SYSTEM

celery/app/utils.py

@@ -115,7 +115,7 @@ class Settings(ConfigurationView):
 
 
 class AppPickler(object):
-    """Old application pickler/unpickler (<= 3.0)."""
+    """Old application pickler/unpickler (< 3.1)."""
 
     def __call__(self, cls, *args):
         kwargs = self.build_kwargs(*args)