copier: add more context to a couple of error messages
copier: add more context to a couple of error messages

copier: when returning an error that we didn't copy any files, wrap that
messages a syscall.ENOENT rather than just returning our own text.

Signed-off-by: Nalin Dahyabhai <f562fcb2a0b898bf0be1afc867ea92325d8f825f@redhat.com>

nalind/buildah-1,TomSweeneyRedHat/buildah,rhatdan/buildah,TomSweeneyRedHat/buildah,rhatdan/buildah,TomSweeneyRedHat/buildah,nalind/buildah,nalind/buildah,projectatomic/buildah,projectatomic/buildah,rhatdan/buildah,nalind/buildah-1,projectatomic/buildah,nalind/buildah-1