Error message to improve at bank statement import

After creating a new DB with module account_statement_base_import, if I try to import a bank statement (cf attachement) with lines dated from a previous fy not created in my db then I get a message that could be improve :

*****************************************************************************************************************************
Erreur d'import de relevé

The statement cannot be created: Error: except_osv
Description: (u'Erreur!', u"Il n'y a pas de p\xe9riode d\xe9finie pour cette date : 2013-02-28 00:00:00\nMerci d'en cr\xe9er une.")
Traceback: File "/home/fclementi/openerp-instances/7ocb/parts/bank-statement-reconcile/account_statement_base_import/statement.py", line 185, in statement_import
context)
File "/home/fclementi/openerp-instances/7ocb/parts/bank-statement-reconcile/account_statement_base_import/statement.py", line 123, in prepare_statetement_lines_vals
context=context)
File "/home/fclementi/openerp-instances/7ocb/parts/addons/account/account.py", line 1034, in find
raise osv.except_osv(_('Error!'), _('There is no period defined for this date: %s.\nPlease create one.')%dt)*****************************************************************************************************************************

thx

frederic