I face the same problems as described in Issue 679 for rauc convert when I try to run rauc resign within a container.

rauc-Message: 11:53:21.277: Failed to resolve realpath for '/dev/disk/by-partuuid/615cd737-6106-41f5-a8be-09edc57e8a3e'

For rauc convert the option --trust-environment was introduced to fix this problem I think this might be also a valuable option for rauc resign.