Remove use of callable() from pickle to silence warnings under -3.

Lib/pickle.py

@@ -351,7 +351,7 @@ class Pickler:
             raise PicklingError("args from reduce() should be a tuple")
 
         # Assert that func is callable
-        if not callable(func):
+        if not hasattr(func, '__call__'):
             raise PicklingError("func from reduce should be callable")
 
         save = self.save