As the error appears to originate in SoftwareProperties.py, which belongs to update-manager, I'm moving this to that package.
** Changed in: synaptic (Ubuntu) Sourcepackagename: synaptic => update-manager -- Cannot open Repositories panel in Synaptic Package Manager https://launchpad.net/bugs/50441 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs