The importer is looking for a value for the --copy-children option during a copy operation, but that option is no longer present in the CLI.
Preethi, I'm not sure there's much you can do to verify this except make sure the --recursive option is working as you would expect. The former behavior of the --copy-children option is taken care of by --recursive.
[root@ibm-x3550m3-13 ~]# rpm -q pulp-server
[root@ibm-x3550m3-13 ~]# pulp-admin rpm repo copy errata -f rhel6-2 -t rhel-copy --recursive
This command may be exited via ctrl+c without affecting the request.
Waiting to begin...