Creating a virtualenv with preinstalled packages as in requirements.txt

Typically the steps you always takes are:

• git clone <repo>
• cd <repo>
• pip install virtualenv (if you don’t already have virtualenv installed)
• virtualenv venv to create your new environment (called ‘venv’ here)
• source venv/bin/activate to enter the virtual environment
• pip install -r requirements.txt to install the requirements in the current environment