Setting up the virtualenv can take a significant amount of time because it pulls down packages from PyPI. I was surprised that it does not try to use the locally installed packages. One way to speed up the rebuild is to use a local caching mirror of PyPI. This can be accomplished by using devpi.
Step 1: Install devpi package
sudo pip install devpi
Step 2: Add the following lines in your /root/.pip/pip.conf file
[global] index-url = http://localhost:3141/root/pypi/+simple/ extra-index-url = https://pypi.python.org/simple/
From now on, pip will first try to get the package from devpi-server running on your localhost first and if you do not have devpi-server running, will fallback to pypi.python.org .
Step 3: Start the devpi-server on your localhost: devpi-server. Try
installing a few packages or build a virtualenv. The command
devpi-server -start will start the server and put it in background.
TODO - figure out how to start this from init.