Comment 22 for bug 156575

It seems that debug packages are no longer published in the same repo as the normal ones, but in a separate 'debug' subrepo:
So the package is in here:
http://ppa.launchpad.net/linaro-maintainers/overlay/ubuntu/dists/raring/main/binary-armhf/Packages
And the corresponding debug package is in here:
http://ppa.launchpad.net/linaro-maintainers/overlay/ubuntu/dists/raring/main/debug/binary-armhf/Packages

So now you need to list both the PPA and the debug PPA to use the dgbsym packages:
e.g.:
deb http://ppa.launchpad.net/linaro-maintainers/overlay/ubuntu raring main
deb http://ppa.launchpad.net/linaro-maintainers/overlay/ubuntu raring main/debug