ImportError: cannot import name main

[javarchoo]

+ pip install --upgrade pip
Collecting pip
Downloading pip-10.0.0-py2.py3-none-any.whl (1.3MB)
100% |████████████████████████████████| 1.3MB 638kB/s
Installing collected packages: pip
Found existing installation: pip 8.1.1
Not uninstalling pip at /usr/lib/python2.7/dist-packages, outside environment /usr
Successfully installed pip-10.0.0
+ pip install pyOpenSSL==16.2.0
Traceback (most recent call last):
File "/usr/bin/pip", line 9, in
from pip import main
ImportError: cannot import name main

pypa/pip#5221