Do yourself a favor and install virtualenvwrapper

pip install --user virtualenvwrapper

insert this into your .bashrc

export WORKON_HOME=$HOME/.virtualenvs
export PROJECT_HOME=$HOME/src
source $HOME/.local/bin/virtualenvwrapper.sh

Create your own personal fork of cobbler on github, then clone that one and add a remote for cobbler

git clone https://github.com/eb4x/cobbler.git
cd cobbler/
git config --global user.name "Erik Berg"
git config user.email "c...@slipsprogrammor.no"
git remote add cobbler https://github.com/cobbler/cobbler.git
git fetch cobbler
git pull cobbler master
git branch mynewfeature

mkvirtualenv cobbler
workon cobbler