Не удалось установить Emacs 24 из ppa: cassou / emacs

Я выполнил следующие инструкции по установке Emacs 24 на моем компьютере (заимствован из: http://www.mikeyboldt.com/2011/11/30/install-emacs-24-in-ubuntu/ ):

sudo add-apt-repository ppa:cassou/emacs
sudo apt-get update
sudo apt-get install emacs-snapshot

Но я получаю следующие ошибки:

Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
emacs-snapshot : Depends: libgnutls26 (>= 2.12.6.1-0) but 2.10.5-1ubuntu3 is to be installed
Depends: libmagickcore4 (>= 8:6.6.9.7) but it is not installable
Depends: libmagickwand4 (>= 8:6.6.9.7) but it is not installable
E: Unable to correct problems, you have held broken packages.