pip install looks at http://pypi.python.org/simple/<package>/
You might see the following error in case the connection to pypi.python.org is not open to access (e.g. because of your firewall rules).
Retrying (Retry(total=4, connect=None, read=None, redirect=None)) after connection broken by 'ProtocolError('Connection aborted.', error(111, 'Connection refused'))': /simple/<package>/
The -v option (enabling debug logging/verbose mode is a nice way to start debugging).
Often companies create a proxy to http://pypi.python.org/simple so all the internal sites can access it when they are not exposed to internet.
We can configure this url in pip.conf. By default pip looks into $HOME/.pip/pip.conf for configuration data.
[global]
extra-index-url = https://my-pypi.mywebsite.com/simple
timeout = 10
If you have set the conf and yet if the pip conf is not being picked check that pip.conf is in the right home directory for the user.
e.g.
/root, / or /home/user