在Python中安装软件包时出现pip install tr​​aceback错误

我在使用'pip'安装python软件包时遇到问题，直到几天前我都没有问题，但是现在突然间，每次我想要安装某些东西时，我都会遇到下面的错误. 我在Windows上使用的是Python 2.7，并且已经通过相同的方式重新安装了"pip".

I'm having issues to install python packages using 'pip', i have no problems until a couple of days ago, but now suddenly I have the error below every time i want to install something. I'm using Python 2.7 on windows, and I already reinstall 'pip' by still the same.

Traceback (most recent call last):   
   File "C:\Python27\Scripts\pip-script.py", line 9, in <module>
   load_entry_point('pip==1.5.6', 'console_scripts', 'pip')()

  File "build\bdist.win32\egg\pkg_resources.py", line 339, in load_entry_point
    ns.clear()

  File "build\bdist.win32\egg\pkg_resources.py", line 2470, in load_entry_point
    else:

  File "build\bdist.win32\egg\pkg_resources.py", line 2184, in load
    raise ValueError

  File "C:\Python27\lib\site-packages\pip\__init__.py", line 11, in <module>
    from pip.vcs import git, mercurial, subversion, bazaar  # noqa

  File "C:\Python27\lib\site-packages\pip\vcs\mercurial.py", line 9, in <module>
    from pip.download import path_to_url

  File "C:\Python27\lib\site-packages\pip\download.py", line 26, in <module>
    from requests.compat import IncompleteRead

ImportError:无法导入名称IncompleteRead

ImportError: cannot import name IncompleteRead