Comment # 3 on bug 1175984 from Ulrich Windl

(In reply to Fabian Vogt from comment #2)
> Sounds like you added the 15.1 DVD as repo some time ago and didn't remove
> it before running zypper dup. If you didn't do it manually, YaST probably
> did it during install. IIRC it's supposed to remove it later though.

In the past I had upgraded via local DVD medium, so the medium is present in
the repositories, and no, I did not deactivate the DVD repository.