See also issue3657. For some reasons, C bound methods aliased as module globals can be pickled, but not similarly aliased Python bound methods:
>>> random.random, random.seed
(<built-in method random of Random object at 0x27abe20>, <bound method Random.seed of <random.Random object at 0x27abe20>>)
>>> pickle.dumps(random.random)
b'\x80\x03crandom\nrandom\nq\x00.'
>>> pickle.dumps(random.seed)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/antoine/py3k/__svn__/Lib/pickle.py", line 1314, in dumps
Pickler(f, protocol, fix_imports=fix_imports).dump(obj)
_pickle.PicklingError: Can't pickle <class 'method'>: attribute lookup builtins.method failed