1 files changed, 6 insertions, 3 deletions
diff --git a/Lib/multiprocessing/util.py b/Lib/multiprocessing/util.py
index b490caa..f0827f0 100644
--- a/Lib/multiprocessing/util.py
+++ b/Lib/multiprocessing/util.py
@@ -149,12 +149,15 @@ class Finalize(object):
     Class which supports object finalization using weakrefs
     '''
     def __init__(self, obj, callback, args=(), kwargs=None, exitpriority=None):
-        assert exitpriority is None or type(exitpriority) is int
+        if (exitpriority is not None) and not isinstance(exitpriority,int):
+            raise TypeError(
+                "Exitpriority ({0!r}) must be None or int, not {1!s}".format(
+                    exitpriority, type(exitpriority)))
 
         if obj is not None:
             self._weakref = weakref.ref(obj, self)
-        else:
-            assert exitpriority is not None
+        elif exitpriority is None:
+            raise ValueError("Without object, exitpriority cannot be None")
 
         self._callback = callback
         self._args = args