- "yum update" fails because yum tries to download yum-2.0.4-3.noarch.rpm from ftp://<mirror>/fedora.redhat.com/pub/fedora/linux/core/development/s390s/Fedora/RPMS/, not from ftp://<mirror>/fedora.redhat.com/pub/fedora/linux/core/development/i386/Fedora/RPMS/. Not many mirrors actually carry the s390x stuff.
- After upgrading to yum-2.0.4-3 manually (downloading the rpm, rpm -Fvh), it didn't work. I had rpm-python-4.2.1-0.30, not rpm-python-4.2.1-0.30.1. After upgrading that it worked. I think yum.rpm should have a dependency to the new version...