Handle AR exceptions gracefully when a new Catalog item is created

A call to create_request might lead to AR exceptions in the model that need to be rescued and passed on to the controller.

https://bugzilla.redhat.com/show_bug.cgi?id=1095457
This looks great, but flash messaging all errors from an active record model does seem pretty common.

Is there already a helper that does this? /cc @dclarizio