Return packingnumber hardcoded {'name':'%s (return)' % pick.name

As of version 5.0.8 the returnpacking number contains the hardcoded part in it's number "(return)
See addons/stock/wizard/wizard_return.py line 83
            new_picking = pick_obj.copy(cr, uid, pick.id, {'name':'%s (return)' % pick.name,
                    'move_lines':[], 'state':'draft', 'type':new_type,
                    'date':date_cur, 'invoice_state':data['form']['invoice_state'],})

This does greatly enhance the visibility, but has a side effect when the number is used for internal barcode (EAN13) generation.
The "(" and ")" signs are used for start/end char in the barcode generation, hence the generations fails.

Quick fix is to rename the part of {'name':'%s (return)' to {'name':'%s-return'
The better option is to make use of a separate sequence generator for returnpickings where the suffix can be used.

I guess the same issue is for V6