Comment # 6 on bug 939456 from Mateusz Mielczarek

(In reply to Steffen Winterfeldt from comment #3)
> Chris, you can run the tumbleweed iso through mksusecd
> (software.opensuse.org).
> This will give you a working iso. (mksusecd -c new.iso old.iso)

I tried that methon, but don't work for me (I tried under the arch linux)

arch:~/Documents/git/mksusecd sysek$ sudo ./mksusecd -c new-opensuse.iso
openSUSE-Tumbleweed-NET-x86_64-Snapshot20150728-Media.iso 
El-Torito legacy bootable (x86_64)
El-Torito UEFI bootable (x86_64)
building: 100%
isohybrid: invalid offset: `8344', 0 <= offset <= 64
Error: isohybrid failed