Description of problem:

Error Type: <type 'exceptions.NameError'>
Error Value: global name 'yum' is not defined
  File : /usr/share/PackageKit/helpers/yum/yumBackend.py, line 2280, in <module>
    main()
  File : /usr/share/PackageKit/helpers/yum/yumBackend.py, line 2276, in main
    backend = PackageKitYumBackend('', lock=True)
  File : /usr/share/PackageKit/helpers/yum/yumBackend.py, line 191, in __init__
    if not self.comps.connect():
  File : /usr/share/PackageKit/helpers/yum/yumComps.py, line 233, in connect
    self._make_database_tables()
  File : /usr/share/PackageKit/helpers/yum/yumComps.py, line 250, in _make_database_tables
    self.refresh()
  File : /usr/share/PackageKit/helpers/yum/yumComps.py, line 260, in refresh
    except yum.Errors.RepoError, e:


Version-Release number of selected component (if applicable):
PackageKit-yum-0.3.12-1.fc10.i386

Additional info:
yum is only imported in main but used in lib.

If the __main__ part had been placed in a main() function instead of conditionally in the global namespace then pylint would have caught this.