When check the latest package, get No package list available message.

Issue

The following messages are displayed when carry out yum on redhat registered as a system of the customer portal and fail in the acquisition of the list of update.

What is the root cause ?

# yum update list
Loaded plugins: product-id, refresh-packagekit, security, subscription-manager
This system is receiving updates from Red Hat Subscription Management.
rhel-6-server-cf-tools-1-rpms | 2.8 kB 00:00
rhel-6-server-rhev-agent-rpms | 3.1 kB 00:00
rhel-6-server-rpms | 3.7 kB 00:00
Setting up Update Process
No Match for argument: list
No package list available.
No Packages marked for Update