@classmethod<EOL><INDENT>def email_on_invoice_change(cls, invoice, old_status, new_status):<DEDENT>
<EOL>silent_status = [<EOL>commerce.Invoice.STATUS_VOID,<EOL>commerce.Invoice.STATUS_UNPAID,<EOL>]<EOL>if old_status == new_status:<EOL><INDENT>return<EOL><DEDENT>if False and new_status in silent_status:<EOL><INDENT>pass<EOL><DEDENT>cls.email(invoice, "<STR_LIT>")<EOL>
Sends out all of the necessary notifications that the status of the
        invoice has changed to:

        - Invoice is now paid
        - Invoice is now refunded