RPIO is used to provide the hardware PWM signals to drive the ESCs.
Before you can use any of the Python code for your quadcopter, you need to install and build RPIO:
sudo apt-get install gcc python-dev python-setuptools
git clone https://github.com/metachris/RPIO.git
sudo python setup.py install
Once it’s installed, make sure you have the quadcopter python code from 26 January 2014 (or later) – it includes additional function to stop all the debug logging from RPIO which can inhibit performance and smother your screen with debug logs.