spacewalk-create-channel fails to create child channels

Issue

• Can create a new base channel using spacewalk-create-channel, but receiving an error while attempting to create child channels:

        $ spacewalk-create-channel --user=admin --server=$HOSTNAME --version=6 --update=u1 --release=Server --arch=x86_64 --extra=Supplementary --parent=mychannel-rhel6_1 --destChannel=mychannel-rhel6_1-supplementary
        [...]
        You have not specified a source channel, we will try to determine it from inputs
        Trying with source channel: rhel-x86_64-server-supplementary-6
        Error: Source Channel 'rhel-x86_64-server-supplementary-6' could not be found.