Trying to upgrade a SLES11SP4 VM running on ESXi 6.0 to SLES12SP1 by
booting from the ISO and selecting Upgrade.

The upgrade goes well until it comes to Installing
libbrlapi0_6-5.1-7.29.x86_64.rpm (installed size 123.9 KiB)

At this point the CPU usage goes to 100% and nothing else happens, it is
just stuck, I've waited for about 20 minutes before reverting to a snapshot.

Any tips on how to proceed?