/var/log/gofer/agent.log says:
==================

2012-04-02 16:04:13,611 [INFO][worker-0] dispatch() @ dispatcher.py:530 - dispatching:{
  "args": [
    [
      "zsh"
    ], 
    false
  ], 
  "auth": {
    "secret": "34259164a98e78816ff69c803fe7f293d876357bd903c3475f456e773274d93c", 
    "pam": null, 
    "uuid": "23c46ae4-fe3b-42ec-8125-a45bf1260dd4"
  }, 
  "classname": "Packages", 
  "kws": {}, 
  "cntr": [
    [], 
    {
      "importkeys": false
    }
  ], 
  "method": "install"
}
2012-04-02 16:04:13,635 [ERROR][worker-0] __call__() @ dispatcher.py:488 - Values instance has no attribute 'repos'
Traceback (most recent call last):
  File "/usr/lib/python2.6/site-packages/gofer/rmi/dispatcher.py", line 485, in __call__
    retval = method(*args, **keywords)
  File "/usr/lib64/gofer/plugins/katelloplugin.py", line 175, in install
    installed = p.install(names)
  File "/usr/lib64/gofer/plugins/package.py", line 176, in install
    yb.install(pattern=info)
  File "/usr/lib/python2.6/site-packages/yum/__init__.py", line 3338, in install
    mypkgs = self.pkgSack.returnPackages(patterns=pats,
  File "/usr/lib/python2.6/site-packages/yum/__init__.py", line 882, in <lambda>
    pkgSack = property(fget=lambda self: self._getSacks(),
  File "/usr/lib/python2.6/site-packages/yum/__init__.py", line 668, in _getSacks
    self.repos.populateSack(which=repos)
  File "/usr/lib/python2.6/site-packages/yum/repos.py", line 260, in populateSack
    self.doSetup()
  File "/usr/lib/python2.6/site-packages/yum/repos.py", line 72, in doSetup
    self.ayum.plugins.run('prereposetup')
  File "/usr/lib/python2.6/site-packages/yum/plugins.py", line 184, in run
    func(conduitcls(self, self.base, conf, **kwargs))
  File "/usr/share/yum-plugins/rhnplugin.py", line 197, in prereposetup_hook
    for opt, repoexp in opts.repos:
AttributeError: Values instance has no attribute 'repos'
2012-04-02 16:04:13,636 [INFO][worker-0] sendreply() @ rmi.py:158 - b97ed0b4-dabb-4839-bfa6-a4cce627a8a9 processed in: 88 (ms)

I tried to install packages via yum on registered client node. I can pull the packages via yum.

[root@dhcp201-130 ~]# yum install zsh
Loaded plugins: product-id, rhnplugin, subscription-manager
Updating certificate-based repositories.
rhel-6-server-rpms                                       | 3.7 kB     00:00     
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package zsh.x86_64 0:4.3.10-4.1.el6 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

================================================================================
 Package    Arch          Version               Repository                 Size
================================================================================
Installing:
 zsh        x86_64        4.3.10-4.1.el6        rhel-6-server-rpms        2.1 M

Transaction Summary
================================================================================
Install       1 Package(s)

Total download size: 2.1 M
Installed size: 2.1 M
Is this ok [y/N]: y
Downloading Packages:
zsh-4.3.10-4.1.el6.x86_64.rpm                            | 2.1 MB     00:00     
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
Warning: RPMDB altered outside of yum.
  Installing : zsh-4.3.10-4.1.el6.x86_64                                    1/1 
Installed products updated.

Installed:
  zsh.x86_64 0:4.3.10-4.1.el6                                                   

Complete!
[root@dhcp201-130 ~]# cat /etc/yum.repos.d/redhat.repo 
#
# Certificate-Based Repositories
# Managed by (rhsm) subscription-manager
#

[rhel-6-server-rpms]
name = Red Hat Enterprise Linux 6 Server (RPMs)
baseurl = https://dhcp201-142.englab.pnq.redhat.com/pulp/repos/ACME_Corporation/stage/content/dist/rhel/server/6/$releasever/$basearch/os
enabled = 1
gpgcheck = 1
gpgkey = file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release
sslverify = 1
sslcacert = /etc/rhsm/ca/candlepin-ca.pem
sslclientkey = /etc/pki/entitlement/7238643478145594779-key.pem
sslclientcert = /etc/pki/entitlement/7238643478145594779.pem
[root@dhcp201-130 ~]#

# COMMENT

some note that may be helpful (maybe not) ;)
---
katello-0.2.24-1.git.7.0b241dc.el6.noarch
katello-agent-1.0.3-1.git.0.cccd0b4.el6.noarch
yum-3.2.29-22.el6_2.2.noarch
subscription-manager-0.99.8-1.el6.x86_64
gofer-0.67-1.el6.noarch
python-rhsm-0.99.6-1.el6.noarch
python-gofer-0.67-1.el6.noarch
gofer-package-0.67-1.el6.noarch

I did prepared a scenario (with having GPG signed repo) and the CLI-way of `system packages --install lion` just got fine.

My Bad.. The client machine was registered with rhn..By disbaling the rhn plugin (/etc/yum/pluginconf.d/rhnplugin.conf) resolved this issue..

--


[root@dhcp201-130 ~]# tail -f /var/log/gofer/agent.log 
  "classname": "Packages", 
  "kws": {}, 
  "cntr": [
    [], 
    {
      "importkeys": false
    }
  ], 
  "method": "install"
}
2012-04-04 19:41:17,434 [INFO][worker-0] install() @ katelloplugin.py:176 - Packages installed: {'resolved': [{'epoch': '0', 'version': '4.3.10', 'name': 'zsh', 'release': '4.1.el6', 'arch': 'x86_64', 'qname': 'zsh-4.3.10-4.1.el6.x86_64', 'repoid': 'rhel-6-server-rpms'}], 'deps': []}
2012-04-04 19:41:17,435 [INFO][worker-0] sendreply() @ rmi.py:158 - d036330e-2412-4ae0-b750-19e04b77a038 processed in: 26.123 (seconds)