Description of problem:
system-config-kickstart fails when used with non-fedora yum configuration.

Version-Release number of selected component (if applicable):
2.7.12-1.fc8

How reproducible:
Always.

Steps to Reproduce:
1. Remove all Fedora yum configuration
2. run system-config-kickstart
  
Actual results:
Loading "priorities" plugin
0 packages excluded due to repository priority protections
Component: system-config-kickstart
Summary: TB2b74954f packages.py:143:__init__:AttributeError: 'module' object has
no attribute 'Error'

Traceback (most recent call last):
  File "/usr/bin/system-config-kickstart", line 83, in <module>
    kickstartGui.kickstartGui(file)
  File "/usr/share/system-config-kickstart/kickstartGui.py", line 167, in __init__
    self.packages_class = packages.Packages(xml, self.ksHandler)
  File "/usr/share/system-config-kickstart/packages.py", line 181, in __init__
    self.y = sckYumBase(pbar)
  File "/usr/share/system-config-kickstart/packages.py", line 143, in __init__
    except yum.Error.RepoError:
AttributeError: 'module' object has no attribute 'Error'

Local variables in innermost frame:
repo: development
tempfile: <module 'tempfile' from '/usr/lib/python2.5/tempfile.pyc'>
self: <packages.sckYumBase object at 0xa88496c>
repoorder: ['development', 'fedora']
callback: <pirut.Progress.PirutProgressCallback instance at 0xa88472c>


Expected results:
Workingness.

Additional info:
Patch included.