TypeError: unsupported operand type(s) for -=: 'Retry' and 'int'

Collecting pip
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 328, in run
    wb.build(autobuilding=True)
  File "/usr/lib/python2.7/dist-packages/pip/wheel.py", line 748, in build
    self.requirement_set.prepare_files(self.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 577, in _prepare_file
    session=self.session, hashes=hashes)
  File "/usr/lib/python2.7/dist-packages/pip/download.py", line 810, in unpack_url
    hashes=hashes
  File "/usr/lib/python2.7/dist-packages/pip/download.py", line 649, in unpack_http_url
    hashes)
  File "/usr/lib/python2.7/dist-packages/pip/download.py", line 842, in _download_http_url
    stream=True,
  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'
You are using pip version 8.1.1, however version 19.0.3 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.      

解決辦法：

apt-get remove python-pip python3-pip
wget https://bootstrap.pypa.io/get-pip.py
 
python get-pip.py
python3 get-pip.py