Uninformative error when docker fails

[dlipovetsky]

# /opt/bin/nodeadm init --cfg /etc/nodeadm.yaml
INFO[0000] Setting masterConfiguration.api.bindPort to 6443 
FATA[0002] failed to run "docker load -i /var/cache/nodeadm/images/18d31d4ba9ad3d8eb6a5abf53d907fa7501cb0fd2f2703a2bab3197a9ad186cc.tar": exit status 1 

The cause turned out to be a corrupted tarball:

# docker load -i /var/cache/nodeadm/images/18d31d4ba9ad3d8eb6a5abf53d907fa7501cb0fd2f2703a2bab3197a9ad186cc.tar
fe9a8b4f1dcc: Loading layer [==================================================>]  43.87MB/43.87MB
invalid diffID for layer 0: expected "sha256:fe9a8b4f1dccd77105b8423a26536ff756f1ee99fdcae6893eb737ae1c527c7a", got "sha256:980b894612821b59edd3580d5f4358ff828a4e2bdc70840a82ecdf45fcaba38c"

cctl should relay the error message along with the exit code.