python 运行脚本报错 from keyword import iskeyword as _iskeyword ImportError: cannot import name iskeyword，说明python环境坏了，得重装，尚不知具体原因，

C:\Python27\Scripts>python task_test.py
Traceback (most recent call last):
  File "task_test.py", line 2, in <module>
    import unittest
  File "C:\Python27\lib\unittest\__init__.py", line 58, in <module>
    from .result import TestResult
  File "C:\Python27\lib\unittest\result.py", line 9, in <module>
    from . import util
  File "C:\Python27\lib\unittest\util.py", line 2, in <module>
    from collections import namedtuple, OrderedDict
  File "C:\Python27\lib\collections.py", line 22, in <module>
    from keyword import iskeyword as _iskeyword
ImportError: cannot import name iskeyword

我在装lettuce之后，运行lettuce发现报错，再然后运行其他脚本也报这个错，替换了别人的好用的python目录，也不行，重装就好了