When importing with manage-marc-import.pl it doesn't tell if some information in the records which it is processing is missing some info / or the info is invalid.

In bug 14762 there was the problem with invalid itemtype code. We should give at least some warning if the user tries to import data to Koha which is not compatible with the preferences the user has set in Koha (for example, the data to be imported has an itemtype code of X but the system doesn't have that code). 

It would be even better if we could put there some suggestion that says, for example, that "The itemtype code used in your imported data doesn't exists in the system, do you want to create it / do you want to change the itemtype codes of the data you're importing"