Virtualenv - RuntimeWarning: invalid Python installation

If you put your virtualenv environment inside /usr/local , you will see this error when running pip install something, for example:

RuntimeWarning: invalid Python installation: unable to open /usr/share/.venv/yl/lib/python2.7/config/Makefile (No such file or directory)

To fix this, just move your virtualenv environment outside of /usr/local !