Jeremy writes:

I found the following patch helpful in tracking down a bug in some
code.  I had appended time, the module, instead of time.time().  Not
sure if it is generally true that printing the repr of the object is
good, but I expect that most unpicklable things will have fairly
information and concise reprs (like files or sockets or modules).

Lib/pickle.py

@@ -157,7 +157,8 @@ def save(self, object, pers_save = 0):
                     reduce = object.__reduce__
                 except AttributeError:
                     raise PicklingError, \
-                        "can't pickle %s objects" % `t.__name__`
+                        "can't pickle %s object: %s" % (`t.__name__`,
+                                                         `object`)
                 else:
                     tup = reduce()
             else: