F23 installer does not allow to reuse / partition

[Chris Murphy]

If you haven't tried using 'strace mkfs.<fs>" it's very educational.
All it does is write some stuff to the disk. It's mostly zeros, but
also the signature, UUID, stuff that makes up the superblocks. The
fact this fails, suggest the device can't even handle basic writes. So
there's no reason to believe that the installer would have any success
installing the OS to such a device.

I'd expect there are kernel messages if mkfs fails - most likely write
failure to specific sectors.

Chris Murphy