cp failure uses confusing error message

[apostasie]

Description

Destination of the copy being read-only:

nerdctl cp buildkitd:/usr/bin/buildctl .
/usr/bin/tar: buildctl: Cannot open: Read-only file system
/usr/bin/tar: Exiting with failure status due to previous errors
FATA[0000] could not find container: buildkitd, with error: failed to wait [/usr/bin/tar -x --no-same-owner -f -]: exit status 2

Of course the container buildkitd is here and fine.

We should clean-up this above and provide a helpful message to the user instead.

Good first issue.

Steps to reproduce the issue

na

Describe the results you received and expected

na

What version of nerdctl are you using?

main

Are you using a variant of nerdctl? (e.g., Rancher Desktop)

None

Host information

No response