Description of problem:
I was trying to remove a package 'zsh' from a system and this package was not installed. However UI was still scheduling the package removal.

Following notification generated:

2011-12-20 11:40:12 	success 	Uninstall of Packages 'zsh' scheduled for System 'dhcp201-204.englab.pnq.redhat.com'.

agent.log says:
===============
2011-12-20 17:10:11,587 [INFO][worker-0] dispatch() @ dispatcher.py:530 - dispatching:{
  "args": [
    [
      "zsh"
    ]
  ], 
  "auth": {
    "secret": null, 
    "pam": null, 
    "uuid": "31556e3b-8d32-4b0b-a5d9-0dc388fcef17"
  }, 
  "classname": "Packages", 
  "kws": {}, 
  "cntr": null, 
  "method": "uninstall"
}
2011-12-20 17:10:11,843 [INFO][worker-0] uninstall() @ katelloplugin.py:180 - Packages uninstalled: []


Version-Release number of selected component (if applicable):
[root@dhcp201-123 ~]# rpm -qa | grep katello
katello-glue-candlepin-0.1.143-2.el6.noarch
katello-cli-common-0.1.25-2.el6.noarch
katello-qpid-broker-key-pair-1.0-1.noarch
katello-certs-tools-1.0.1-2.el6.noarch
katello-glue-pulp-0.1.143-2.el6.noarch
katello-all-0.1.143-2.el6.noarch
katello-trusted-ssl-cert-1.0-1.noarch
katello-configure-0.1.37-2.el6.noarch
katello-common-0.1.143-2.el6.noarch
katello-0.1.143-2.el6.noarch
katello-cli-0.1.25-2.el6.noarch
katello-glue-foreman-0.1.143-2.el6.noarch
katello-httpd-ssl-key-pair-1.0-1.noarch


How reproducible:
always

Steps to Reproduce:
1. Try to remove a package which is not installed.

  
Actual results:
2011-12-20 11:40:12 	success 	Uninstall of Packages 'zsh' scheduled for System 'dhcp201-204.englab.pnq.redhat.com'.


Expected results:
A proper warning message should be generated saying that "The selected package is not installed on the system."


Additional info: