pip win10 升级问题

python -m pip install --upgrade pip

问题：
Collecting pip
  Using cached pip-9.0.1-py2.py3-none-any.whl
Installing collected packages: pip
  Found existing installation: pip 8.1.2
    Uninstalling pip-8.1.2:
      Successfully uninstalled pip-8.1.2
  Rolling back uninstall of pip
Exception:
Traceback (most recent call last):
  File "D:\python3.5.2\lib\site-packages\pip-8.1.2-py3.5.egg\pip\basecommand.py", line 215, in main
    status = self.run(options, args)
  File "D:\python3.5.2\lib\site-packages\pip-8.1.2-py3.5.egg\pip\commands\install.py", line 317, in run
    prefix=options.prefix_path,
  File "D:\python3.5.2\lib\site-packages\pip-8.1.2-py3.5.egg\pip\req\req_set.py", line 742, in install
    **kwargs
  File "D:\python3.5.2\lib\site-packages\pip-8.1.2-py3.5.egg\pip\req\req_install.py", line 831, in install
    self.move_wheel_files(self.source_dir, root=root, prefix=prefix)
  File "D:\python3.5.2\lib\site-packages\pip-8.1.2-py3.5.egg\pip\req\req_install.py", line 1032, in move_wheel_files
    isolated=self.isolated,
  File "D:\python3.5.2\lib\site-packages\pip-8.1.2-py3.5.egg\pip\wheel.py", line 463, in move_wheel_files
    generated.extend(maker.make(spec))
  File "D:\python3.5.2\lib\site-packages\pip-8.1.2-py3.5.egg\pip\_vendor\distlib\scripts.py", line 372, in make
    self._make_script(entry, filenames, options=options)
  File "D:\python3.5.2\lib\site-packages\pip-8.1.2-py3.5.egg\pip\_vendor\distlib\scripts.py", line 276, in _make_script
    self._write_script(scriptnames, shebang, script, filenames, ext)
  File "D:\python3.5.2\lib\site-packages\pip-8.1.2-py3.5.egg\pip\_vendor\distlib\scripts.py", line 212, in _write_script
    launcher = self._get_launcher('t')
  File "D:\python3.5.2\lib\site-packages\pip-8.1.2-py3.5.egg\pip\_vendor\distlib\scripts.py", line 351, in _get_launcher
    result = finder(distlib_package).find(name).bytes
AttributeError: 'NoneType' object has no attribute 'bytes'
You are using pip version 8.1.2, however version 9.0.1 is available.
You should consider upgrading via the 'python -m pip install --upgrade pip' command.

You are using pip version 8.1.2, however version 9.0.1 is available.
You should consider upgrading via the 'python -m pip install --upgrade pip' command.
解决方法：

python -m pip install -U --force-reinstall pip

Collecting pip
  Using cached pip-9.0.1-py2.py3-none-any.whl
Installing collected packages: pip
  Found existing installation: pip 9.0.1
    Uninstalling pip-9.0.1:
      Successfully uninstalled pip-9.0.1
Successfully installed pip-9.0.1

参考https://github.com/pypa/pip/issues/2669