我刚刚重新安装了ubuntu 14.04LTS，但我尝试使用pip，但得到以下回溯：

(nlmanagement)psychok7@Ultrabook:~/code/work/nlmanagement$ pip freeze
Traceback (most recent call last):
  File "/home/psychok7/code/work/venv/nlmanagement/bin/pip", line 9, in <module>
    load_entry_point('pip==1.1', 'console_scripts', 'pip')()
  File "/home/psychok7/code/work/venv/nlmanagement/local/lib/python2.7/site-packages/distribute-0.6.24-py2.7.egg/pkg_resources.py", line 337, in load_entry_point
    return get_distribution(dist).load_entry_point(group, name)
  File "/home/psychok7/code/work/venv/nlmanagement/local/lib/python2.7/site-packages/distribute-0.6.24-py2.7.egg/pkg_resources.py", line 2279, in load_entry_point
    return ep.load()
  File "/home/psychok7/code/work/venv/nlmanagement/local/lib/python2.7/site-packages/distribute-0.6.24-py2.7.egg/pkg_resources.py", line 1989, in load
    entry = __import__(self.module_name, globals(),globals(), ['__name__'])
  File "/home/psychok7/code/work/venv/nlmanagement/local/lib/python2.7/site-packages/pip-1.1-py2.7.egg/pip/__init__.py", line 10, in <module>
    from pip.backwardcompat import walk_packages, console_to_str
  File "/home/psychok7/code/work/venv/nlmanagement/local/lib/python2.7/site-packages/pip-1.1-py2.7.egg/pip/backwardcompat.py", line 77, in <module>
    from urllib2 import URLError, HTTPError
  File "/usr/lib/python2.7/urllib2.py", line 94, in <module>
    import httplib
  File "/usr/lib/python2.7/httplib.py", line 79, in <module>
    import mimetools
  File "/usr/lib/python2.7/mimetools.py", line 6, in <module>
    import tempfile
  File "/usr/lib/python2.7/tempfile.py", line 32, in <module>
    import io as _io
  File "/usr/lib/python2.7/io.py", line 51, in <module>
    import _io
ImportError: No module named _io

有任何想法吗？？我曾尝试sudo apt-get install python3-pip和sudo apt-get install python- pip