Add a new case to deal with an object item in addWarning

Allows to add some information as item when an object is used in addWarning (case encountered in the PIM product writer).
In fact, it's done on purpose to generate a useable translation key for a step, 
string(55) "pim_base_connector.jobs.csv_product_export.export.title"
string(41) "pim_base_connector.steps.csv_writer.title"