Python pip说:pkg_resources.DistributionNotFound:pip == 1.4.1

我刚刚安装了Ubuntu 14.04并安装了pycharm.Pycharm表示setuptools和pip没有安装并提供安装它.我只需单击"Ÿes",它似乎安装它.之后我想用pip安装Flask(这真是太棒了),所以我做到了sudo pip install flask.令我惊讶的是它说了以下内容:

Traceback (most recent call last):
  File "/usr/local/bin/pip", line 5, in 
    from pkg_resources import load_entry_point
  File "build/bdist.linux-x86_64/egg/pkg_resources.py", line 2797, in 

  File "build/bdist.linux-x86_64/egg/pkg_resources.py", line 576, in resolve
    def resolve(self, requirements, env=None, installer=None,
pkg_resources.DistributionNotFound: pip==1.4.1

所以我只是尝试了常规方法:我下载了get-pip.py并运行了,但是这说: Requirement already up-to-date: pip in /usr/local/lib/python2.7/dist-packages

我在SO上发现了一些其他类似的 问题,建议查看/usr/local/lib/python2.7/site-packages/,但该文件夹是空的.

有人知道什么是错的,我怎么解决这个问题？欢迎所有提示!