openSuse: how to get rid of annoying "Authentication Required" dialog from auto-update

This annoying dialog "Authentication Required" started to pop up recently, just after every login to KDE, demanding root password to refresh system repositories. After a minute or so it disappears on it's own, followed by a "update failed" tray notification, which also disappears soon. It's not a blocker, just annoying and looking unprofessionally. Please, how to get rid of this? It must be something to do with KDE/Gnome interoperability because: * it started to appear only after I had installed Gnome alongside my primary KDE * no Authentication Required pops up when login to Gnome * the dialog looks like it is from Gnome (KDE has a differently looking password UI) The pop-up dialog says (in case you cannot see the screenshot above):

Authentication is required to refresh the system repositories.
Action: Refresh system repositories
        org.freedesktop.packagekit.system-sources-refresh
Vendor: The PackageKit project.
polkit.subject-pid: xxxx
polkit.caller-pid:  xxxx