ssh를 통해 EC2 인스턴스에서 pip 버전을 업데이트 할 수 없음

ssh를 통해 pip 버전 ec2 인스턴스를 업그레이드하려고 할 때 이와 같은 오류가 발생합니다.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/pip/basecommand.py", line 209, in main
    status = self.run(options, args)
  File "/usr/lib/python3/dist-packages/pip/commands/install.py", line 328, in run
    wb.build(autobuilding=True)
  File "/usr/lib/python3/dist-packages/pip/wheel.py", line 748, in build
    self.requirement_set.prepare_files(self.finder)
  File "/usr/lib/python3/dist-packages/pip/req/req_set.py", line 360, in prepare_files
    ignore_dependencies=self.ignore_dependencies))
  File "/usr/lib/python3/dist-packages/pip/req/req_set.py", line 448, in _prepare_file
    req_to_install, finder)
  File "/usr/lib/python3/dist-packages/pip/req/req_set.py", line 397, in _check_skip_installed
    finder.find_requirement(req_to_install, self.upgrade)
  File "/usr/lib/python3/dist-packages/pip/index.py", line 442, in find_requirement
    all_candidates = self.find_all_candidates(req.name)
  File "/usr/lib/python3/dist-packages/pip/index.py", line 400, in find_all_candidates
    for page in self._get_pages(url_locations, project_name):
  File "/usr/lib/python3/dist-packages/pip/index.py", line 545, in _get_pages
    page = self._get_page(location)
  File "/usr/lib/python3/dist-packages/pip/index.py", line 648, in _get_page
    return HTMLPage.get_page(link, session=self.session)
  File "/usr/lib/python3/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/python3/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'