$ sudo apt-get update
$ sudo apt-get install python-gtksourceview2 

python-gtksourceview2 is installed in your system.

Make ensure the python-gtksourceview2 package were installed using the commands given below,

$ sudo dpkg-query -l | grep python-gtksourceview2 *

You will get with python-gtksourceview2 package name, version, architecture and description in a table

python-gtksourceview2 package basic information: