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