Using set key for signature fails

[drahnr]

Setting a key
# yubico-piv-tool --action=generate -A ECCP384 --slot=9c
and subsequently attempting to use it to sign data

yk::certificate::Certificate::read(&mut yk, yk::key::SlotId::Signature)

fails with

Error: invalid object

I did not dig into the details yet :)

[drahnr]

Depending how you want to organize this, could be part #45

[tarcieri]

Will try to reproduce this soon