change message for unfulffiled requirements

[pirat89]

When some module requests specific rpm for correct functionality (to be able to provide full possible check), current message printed by PA is confusing. See mysql/configuration_changes, that is applied when the mysql-libs rpm is installed, but require the mysql rpm for correct checking of configuration.

In case the mysql rpm is not installed, you can see this message:

preupg.risk.HIGH: Package mysql is not installed.
preupg.risk.HIGH: Please, install all required packages (and binaries) and run preupg again to process check properly.

The message should provide better clarification for user, why the package should be installed. Like:

preupg.risk.HIGH: The mysql-libs cannot be checked properly because these required packages are missing: pkg1, pkg2, pkg3, ....
preupg.risk.HIGH: Please, install all required packages for correct run of the module.

That's just draft text. You can choose whatever text you want, that will be clear for user.