I think I've found a problem with downloading packages from melpa-stable (probably the same will be with 'melpa', but I don't know). I tried to build this 'emacs-mmm-mode' package but it failed because <http://stable.melpa.org/packages/mmm-mode-0.5.2.tar> does not exist anymore (because the current version is 0.5.4).
It looks like (I'm absolutely not sure though) once the new version appears on melpa-stable, the previous tarball is being deleted, which makes the current guix recipe of this package unusable. -- Alex
