Description of problem:

# rpm -q PackageKit

PackageKit-0.1.11-0.620.20080401git.fc9.hughsie.i386

#  rpm -q PackageKit-cron
package PackageKit-cron is not installed

# pkcon install PackageKit-cron

resolve runtime was 3.0 seconds
    [=======================...................................]   40%          
Error: internal-error : Error in Package Signatures
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install-package runtime was 12.1 seconds    

# rpm -q PackageKit-cron
package PackageKit-cron is not installed