This will create main dir tree for installation with svn support etc etc

Code:
svn checkout http://pyrit.googlecode.com/svn/trunk/ pyrit_svn
We have just created a dir /pyrit_svn
This will install libs and other stuff needed:

Code:
apt-get install libssl-dev
apt-get install scapy
apt-get install python-dev
Going to build pyrit

Code:
cd pyrit_svn/pyrit
python setup.py build
python setup.py install
Check now if works typing pyrit on a command line.