$ sudo apt-get update
$ sudo apt-get install mercurial-buildpackage 

mercurial-buildpackage is installed in your system.

Make ensure the mercurial-buildpackage package were installed using the commands given below,

$ sudo dpkg-query -l | grep mercurial-buildpackage *

You will get with mercurial-buildpackage package name, version, architecture and description in a table

mercurial-buildpackage package basic information: