Adicionei o casspa ppa, mas quando tento instalar o emacs24 ou o emacs-snapshot, o apt-get parece não encontrar os pacotes certos:
$ sudo add-apt-repository ppa:cassou/emacs
...
$ sudo apt-get update
...
$ sudo apt-get install emacs24 emacs24-el emacs24-common-non-dfsg
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package emacs24
E: Unable to locate package emacs24-el
E: Unable to locate package emacs24-common-non-dfsg
$ sudo apt-get install emacs-snapshot
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package emacs-snapshot is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'emacs-snapshot' has no installation candidate