load-key -L prompt with keyformat=raw on tty prints error thrice

[nabijaczleweli]

System information

Type	Version/Name
Distribution Name	Debian
Distribution Version	Buster
Linux Kernel	4.19.146-1
Architecture	amd64
ZFS Version	0.8.4-2~bpo10+1
SPL Version	0.8.4-2~bpo10+1

Describe the problem you're observing

zfs load-key prints the "Key load error: Cannot enter raw keys on the terminal" error three times.
I'd expect it to do this exactly once, unless it'd tried to read for three encryption roots? Which isn't the case here, and, still,

Describe how to reproduce the problem

nabijaczleweli@tarta:~$ sudo zfs create -o encryption=on -o keylocation=file:///tmp/owo -o keyformat=raw filling/store/nabijaczleweli/encrypted-zfs
nabijaczleweli@tarta:~$ sudo zfs umount filling/store/nabijaczleweli/encrypted-zfs
nabijaczleweli@tarta:~$ sudo zfs unload-key filling/store/nabijaczleweli/encrypted-zfs
nabijaczleweli@tarta:~$ sudo zfs load-key -L prompt filling/store/nabijaczleweli/encrypted-zfs
Key load error: Cannot enter raw keys on the terminal
Key load error: Cannot enter raw keys on the terminal
Key load error: Cannot enter raw keys on the terminal