Python 因 setuptools 而变得一团糟

Question

在与 Python setuptools 混淆后，我无法让 Python 正常工作。此后，我无法运行flexget其他程序，而不会出现此错误：

flexget execute
Traceback (most recent call last):
  File "/usr/local/bin/flexget", line 5, in <module>
    from pkg_resources import load_entry_point
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources.py", line 78, in <module>
    import setuptools._vendor.packaging.version
ImportError: No module named _vendor.packaging.version

或这个：

File "/usr/local/bin/easy_install", line 7, in <module>
    from setuptools.command.easy_install import main
  File "/usr/lib/python2.7/dist-packages/setuptools/__init__.py", line 12, in <module>
    from setuptools.extension import Extension
  File "/usr/lib/python2.7/dist-packages/setuptools/extension.py", line 7, in <module>
    from setuptools.dist import _get_unpatched
  File "/usr/lib/python2.7/dist-packages/setuptools/dist.py", line 18, in <module>
    import pkg_resources
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources.py", line 78, in <module>
    import setuptools._vendor.packaging.version
ImportError: No module named _vendor.packaging.version

有人能帮我解决这个问题吗？