Adds a permission on a view or menu to the backend

            :param permission_name:
                name of the permission to add: 'can_add','can_edit' etc...
            :param view_menu_name:
                name of the view menu to add

def add_permission_view_menu(self, permission_name, view_menu_name):
        """
            Adds a permission on a view or menu to the backend

            :param permission_name:
                name of the permission to add: 'can_add','can_edit' etc...
            :param view_menu_name:
                name of the view menu to add
        """
        if not (permission_name and view_menu_name):
            return None
        pv = self.find_permission_view_menu(
            permission_name,
            view_menu_name
        )
        if pv:
            return pv
        vm = self.add_view_menu(view_menu_name)
        perm = self.add_permission(permission_name)
        pv = self.permissionview_model()
        pv.view_menu_id, pv.permission_id = vm.id, perm.id
        try:
            self.get_session.add(pv)
            self.get_session.commit()
            log.info(c.LOGMSG_INF_SEC_ADD_PERMVIEW.format(str(pv)))
            return pv
        except Exception as e:
            log.error(c.LOGMSG_ERR_SEC_ADD_PERMVIEW.format(str(e)))
            self.get_session.rollback()