~$ sudo pip install virtualenv
The directory '/home/vri1kor/.cache/pip/http' or its parent directory is not owned by the current user and the cache has been disabled. Please check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
The directory '/home/vri1kor/.cache/pip' or its parent directory is not owned by the current user and caching wheels has been disabled. check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
Collecting virtualenv
Exception:
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/pip/basecommand.py", line 209, in main
    status = self.run(options, args)
  File "/usr/lib/python2.7/dist-packages/pip/commands/install.py", line 317, in run
    requirement_set.prepare_files(finder)
  File "/usr/lib/python2.7/dist-packages/pip/req/req_set.py", line 360, in prepare_files
    ignore_dependencies=self.ignore_dependencies))
  File "/usr/lib/python2.7/dist-packages/pip/req/req_set.py", line 512, in _prepare_file
    finder, self.upgrade, require_hashes)
  File "/usr/lib/python2.7/dist-packages/pip/req/req_install.py", line 273, in populate_link
    self.link = finder.find_requirement(self, upgrade)
  File "/usr/lib/python2.7/dist-packages/pip/index.py", line 442, in find_requirement
    all_candidates = self.find_all_candidates(req.name)
  File "/usr/lib/python2.7/dist-packages/pip/index.py", line 400, in find_all_candidates
    for page in self._get_pages(url_locations, project_name):
  File "/usr/lib/python2.7/dist-packages/pip/index.py", line 545, in _get_pages
    page = self._get_page(location)
  File "/usr/lib/python2.7/dist-packages/pip/index.py", line 648, in _get_page
    return HTMLPage.get_page(link, session=self.session)
  File "/usr/lib/python2.7/dist-packages/pip/index.py", line 757, in get_page
    "Cache-Control": "max-age=600",
  File "/usr/share/python-wheels/requests-2.9.1-py2.py3-none-any.whl/requests/sessions.py", line 480, in get
    return self.request('GET', url, **kwargs)
  File "/usr/lib/python2.7/dist-packages/pip/download.py", line 378, in request
    return super(PipSession, self).request(method, url, *args, **kwargs)
  File "/usr/share/python-wheels/requests-2.9.1-py2.py3-none-any.whl/requests/sessions.py", line 468, in request
    resp = self.send(prep, **send_kwargs)
  File "/usr/share/python-wheels/requests-2.9.1-py2.py3-none-any.whl/requests/sessions.py", line 576, in send
    r = adapter.send(request, **kwargs)
  File "/usr/share/python-wheels/CacheControl-0.11.5-py2.py3-none-any.whl/cachecontrol/adapter.py", line 46, in send
    resp = super(CacheControlAdapter, self).send(request, **kw)
  File "/usr/share/python-wheels/requests-2.9.1-py2.py3-none-any.whl/requests/adapters.py", line 376, in send
    timeout=timeout
  File "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/connectionpool.py", line 610, in urlopen
    _stacktrace=sys.exc_info()[2])
  File "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl/urllib3/util/retry.py", line 228, in increment
    total -= 1
TypeError: unsupported operand type(s) for -=: 'Retry' and 'int'