pip install virtualenv, ошибка на ubuntu 15.04

Как решить эту проблему? и как установить pip и virtualenv на ubuntu 15.04

 pip install virtualenv
    Traceback (most recent call last):
      File "/usr/bin/pip", line 9, in <module>
        load_entry_point('pip==1.5.6', 'console_scripts', 'pip')()
      File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 521, in load_entry_point
        return get_distribution(dist).load_entry_point(group, name)
      File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 2632, in load_entry_point
        return ep.load()
      File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 2312, in load
        return self.resolve()
      File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 2318, in resolve
        module = __import__(self.module_name, fromlist=['__name__'], level=0)
      File "/usr/lib/python2.7/dist-packages/pip/__init__.py", line 74, in <module>
        from pip.vcs import git, mercurial, subversion, bazaar  # noqa
      File "/usr/lib/python2.7/dist-packages/pip/vcs/mercurial.py", line 9, in <module>
        from pip.download import path_to_url
      File "/usr/lib/python2.7/dist-packages/pip/download.py", line 25, in <module>
        from requests.compat import IncompleteRead
    ImportError: cannot import name IncompleteRead