Theano 导入错误：没有名为 cPickle 的模块

>>> import theano
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/Library/Python/2.7/site-packages/theano/__init__.py", line 52, in <module>
from theano.gof import (
 File "/Library/Python/2.7/site-packages/theano/gof/__init__.py", line 38, in <module>
from theano.gof.cc import \
File "/Library/Python/2.7/site-packages/theano/gof/cc.py", line 30, in <module>
from theano.gof import link
File "/Library/Python/2.7/site-packages/theano/gof/link.py", line 18, in <module>
from theano.gof.type import Type
File "/Library/Python/2.7/site-packages/theano/gof/type.py", line 17, in <module>
from theano.gof.op import CLinkerObject
File "/Library/Python/2.7/site-packages/theano/gof/op.py", line 25, in <module>
from theano.gof.cmodule import GCC_compiler
File "/Library/Python/2.7/site-packages/theano/gof/cmodule.py", line 8, in <module>
import six.moves.cPickle as pickle
ImportError: No module named cPickle

我相当确定cPickle没有问题。会不会是其他依赖的问题？确实，今天早上我把所有的包都升级了，所以可能会出现版本冲突的情况。尽管如此，在我切换到 theano 的前沿版本后，问题仍然存在。有人能帮我弄清楚吗？

PS：我的开发设备是Macbook Pro 13（2015年初）；我的系统版本是OS X 10.10.5； python版本是2.7.10

=========================== 第二次编辑 ===================== =============

我的 Mac 上似乎安装了最新版本的 6。

YiqundeMacBook-Pro:~ Leo$ pip show six
---
Metadata-Version: 2.0
Name: six
Version: 1.9.0
Summary: Python 2 and 3 compatibility utilities
Home-page: http://pypi.python.org/pypi/six/
Author: Benjamin Peterson
Author-email: [email protected] /cdn-cgi/l/email-protection
License: MIT
Location: /Library/Python/2.7/site-packages
Requires: 

我也遇到了同样的问题升级解决的六个问题：

sudo easy_install --upgrade six