software-properties-gtk requires removal of apturl but crashes

(from synaptic) I was trying to remove software-center and software-properties-gtk. Checking software-properties-gtk required the apturl to be removed but synaptic did not allow me to continue. Unchecking all and checking independently the apturl and apturl common to be removed did the trick.
I then reinstalled apturl without problems.

$ lsb_release -rd
Description: Ubuntu 15.04
Release: 15.04

$ apt-cache policy software-center
software-center:
  Εγκατεστημένα: (κανένα)
  Υποψήφιο: 13.10-0ubuntu6.1
  Πίνακας Έκδοσης:
     13.10-0ubuntu6.1 0
        500 http://gr.archive.ubuntu.com/ubuntu/ vivid-updates/main amd64 Packages
     13.10-0ubuntu6 0
        500 http://gr.archive.ubuntu.com/ubuntu/ vivid/main amd64 Packages

$ apt-cache policy software-properties-gtk
software-properties-gtk:
  Εγκατεστημένα: (κανένα)
  Υποψήφιο: 0.96.4
  Πίνακας Έκδοσης:
     0.96.4 0
        500 http://gr.archive.ubuntu.com/ubuntu/ vivid/main amd64 Packages

$ apt-cache policy apturl
apturl:
  Εγκατεστημένα: (κανένα)
  Υποψήφιο: 0.5.2ubuntu6
  Πίνακας Έκδοσης:
     0.5.2ubuntu6 0
        500 http://gr.archive.ubuntu.com/ubuntu/ vivid/main amd64 Packages