Running "zypper dup" to upgrade from Leap 15.1 to Leap 15.2, I see this:
Retrieving package libicu60_2-ledata-60.2-lp151.2.4.noarch
                                        (1/5485),   6.2 MiB ( 25.7 MiB
unpacked)
Failed to mount cd:/?devices=/dev/disk/by-id/ata-DVDR_PX-750A on
/var/adm/mount/AP_0xSWAmMb: Mounting media failed (mount:
/var/adm/mount/AP_0xSWAmMb: no medium found on /dev/sr0.)

The path comes from:
grep DVD /etc/zypp/repos.d/*
/etc/zypp/repos.d/openSUSE-Leap-15.1-1.repo:baseurl=cd:/?devices=/dev/disk/by-id/ata-DVDR_PX-750A

Why should an upgrade install an old package from 15.1?

Is it due to this?:
The following 12 packages are going to be downgraded:
  libbrlapi0_6 libdcadec0 libfreerdp2 libicu60_2 libicu60_2-ledata
  libopencore-amrnb0 libopencore-amrwb0 librtmp1 libvo-aacenc0 libwinpr2
  virt-what xboard

Even if so, shouldn't the package to downgrade be fetched from the 15.2
repository? I guess it's a newer build at least...