Return a string to be used as the email subject line.

def subject(self):
        """
        Return a string to be used as the email subject line.
        """
        if self.application_name and self.application_version:
            return 'Crash Report - {name} (v{version})'.format(name=self.application_name,
                                                               version=self.application_version)
        else:
            return 'Crash Report'