Comment # 8 on bug 953130 from Stefan Quandt

For me "Checking for file conflicts" just stalled at 57% for >5 minutes without
finishing, hence I needed to kill zypper.

I could resolve this situation by deleting *lots* of different installed
versions of package kernel-source and package kernel-devel.
I don't know why these package versions accumulate over time (and I also
deleted their files once when running out of disk space (which could also have
contributed to the "checking for file conflicts" issue)).