Comment # 9 on bug 953051 from Christian Boltz

echo 'test
> test' | LANG=C grub2-mkpasswd-pbkdf2
Enter password: 
Reenter password: 
PBKDF2 hash of your password is
grub.pbkdf2.sha512.10000.F0D8663DA50B35468EF04DF7D717BFD7E4AAE0794DD14235E549A4E1FB2EF5A321F54E9C807DB6C7EF5D0C3183DCC5BE4E8F5DF92A3ADAB0ECEA163A02D7319D.FC87796BEA2AF6FE51BF86370AD2E162FCA316E66220A1700978EA9F6D19D19E19BC123AA0C8BA0F72DB38961AAB8F3EAD541D8C7497C07BB681C8E4B6C37136


Looks like it works...

I noticed an interesting detail: I tried the console version of YaST - and was
able to set the boot password there. So this bug seems to be specific to the Qt
interface (which still fails with the same error message).