if you fully update your system, then you will get an updated version of apt-sources-list
. This update will update your current list of repos and remove the Calgary mirror due to its inactivity, see also here
Then you restart Synaptic, or reload and use a working mirror and proceed as outlined before to install scribus
Apart from that: please do not remove existing sections (such as games
, or kde, updates, nonfree, xfce4) from a mirror listed in Synaptic. Such a section may
contain a dependency of a package listed in another section, and then that package could not be installed. In general, there is a reason why we have the sections that we have, so "don't fix a working system"