apt-get problem

[salvax]

I have installed apt package for updating but when i start " apt-get upgrade" command, i get that message..

[root@plesk ~]# apt-get upgrade
Reading Package Lists... Done
Building Dependency Tree... Done
The following packages have unmet dependencies:
psa: Obsoletes: psa-key-custom
psa-api-rpc: Obsoletes: psa-agent


What is that packages ? What should i do? It want to remove them..