pip install ImportError: cannot import name main

root@user:~# pip install --no-cache-dir ansible -i http://mirrors.aliyun.com/pypi/simple/ --trusted-host mirrors.aliyun.com
Traceback (most recent call last):
File "/usr/bin/pip", line , in <module>
from pip import main
ImportError: cannot import name main

#!/usr/bin/python
# GENERATED BY DEBIANimport sys# Run the main entry point, similarly to how setuptools does it, but because
# we didn't install the actual entry point from setup.py, don't use the
# pkg_resources API.
from pip import __main__
if __name__ == '__main__':
sys.exit(__main__._main())