This one is written because to install Keepass2 successfully on Ubuntu 15.04 you need to read and search through at least 5 different sources. So without further ado:

Add ppa’s for Keepass indicator plugin:

sudo add-apt-repository ppa:dlech/keepass2-plugins
sudo add-apt-repository ppa:dlech/keepass2-plugins-beta
sudo apt-get update

Second one contains updated version with solved problem of missing libmagickwand5 dependency.