Description of problem:

When "clevis decrypt" fails for some reason, while in the initramfs and called through clevis_luks_unlock_device_by_slot() function call, the error it can produce is sent to /dev/null, which makes it hard to troubleshoot.

I think the error should be printed on the console, or at least saved to some storage and a message printed back to the user for the user to be able to troubleshoot after having manually unlocked the device:

Original code in /usr/bin/clevis-luks-common-functions:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
313 clevis_luks_unlock_device_by_slot() {
 :
326     if ! passphrase="$(printf '%s' "${jwe}" | clevis decrypt 2>/dev/null)" \
 :
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

Proposed minimal enhancement:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
313 clevis_luks_unlock_device_by_slot() {
 :
326     if ! passphrase="$(printf '%s' "${jwe}" | clevis decrypt)" \
 :
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

Fedora 34 code already has this, as part of commit:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
commit f4ed006f16380ad42efe2c70fe66080d0c420144
Author: Sergio Correia <scorreia>
Date:   Thu Mar 18 11:51:03 2021 -0300
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------


Version-Release number of selected component (if applicable):

clevis-luks-15-1.el8.x86_64


How reproducible:

N/A