title: failed in "sudo pip"
body: <p>Please help me.</p>
  
  <ul>
  <li>server : aws ec2</li>
  <li>os : amazon linux</li>
  <li>python version : 2.7.10</li>
  </ul>
  
  <pre>
  $ pip --version
  pip 7.1.2 from /usr/local/lib/python2.7/site-packages (python 2.7)
  </pre>
  
  <p>It's OK.<br/>
  But...</p>
  
  <pre>
  $ sudo pip --version
  Traceback (most recent call last):
    File "/usr/bin/pip", line 5, in 
      from pkg_resources import load_entry_point
    File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 3020, in 
      working_set = WorkingSet._build_master()
    File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 616, in _build_master
      return cls._build_from_requirements(__requires__)
    File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 629, in _build_from_requirements
      dists = ws.resolve(reqs, Environment())
    File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 807, in resolve
      raise DistributionNotFound(req)
  pkg_resources.DistributionNotFound: pip==6.1.1
  </pre>