Pip behind a proxy

Create or edit the pip.ini file to contain the following:

[global] 
trusted-host =  pypi.python.org 
                pypi.org 
                files.pythonhosted.org 
proxy = <protocol>://<proxy>:<proxyport>/

If you are on Linux, don't forget to point to the pip.ini file, if not yet done:

export PIP_CONFIG_FILE=/path/to/pip.ini