Why do I get "No package spacewalk-proxy-management available" when running the configure-proxy.sh script?

Issue

• Unexpected message at the end of the configure-proxy.sh script:

RHN Proxy successfully activated.
Loaded plugins: rhnplugin
This system is receiving updates from RHN Classic or RHN Satellite.
redhat-rhn-proxy-5.6-server-x86_64-6                     | 1.2 kB     00:00
redhat-rhn-proxy-5.6-server-x86_64-6/primary             |  129 B     00:00
Setting up Install Process
No package spacewalk-proxy-management available.
Error: Nothing to do
Installation of package spacewalk-proxy-management failed. Installation interrupted.
RHN Proxy successfully deactivated.