Description of problem:

After an upgrade from version 11 to version 12, the system tried to update packages automatically, it failed for five update. I am enclosing the message of the system:


Traceback (most recent call last):
  File "/usr/share/PackageKit/helpers/yum/yumBackend.py", line 2759, in install_signature
    self.yumbase.getKeyForPackage(pkg, askcb = lambda x, y, z: True)
  File "/usr/lib/python2.6/site-packages/yum/__init__.py", line 4329, in getKeyForPackage
    result = ts.pgpImportPubkey(misc.procgpgkey(info['raw_key']))
  File "/usr/lib/python2.6/site-packages/rpmUtils/transaction.py", line 59, in __getattr__
    return self.getMethod(attr)
  File "/usr/lib/python2.6/site-packages/rpmUtils/transaction.py", line 69, in getMethod
    return getattr(self.ts, method)
AttributeError: 'NoneType' object has no attribute 'pgpImportPubkey'