Ensure that selected flavors (--ROLE-flavor) exist in nova.

def _check_flavors_exist(self, parsed_args):
        """Ensure that selected flavors (--ROLE-flavor) exist in nova."""
        compute_client = self.app.client_manager.compute

        flavors = {f.name: f for f in compute_client.flavors.list()}

        message = "Provided --{}-flavor, '{}', does not exist"

        for target, flavor, scale in (
            ('control', parsed_args.control_flavor,
                parsed_args.control_scale),
            ('compute', parsed_args.compute_flavor,
                parsed_args.compute_scale),
            ('ceph-storage', parsed_args.ceph_storage_flavor,
                parsed_args.ceph_storage_scale),
            ('block-storage', parsed_args.block_storage_flavor,
                parsed_args.block_storage_scale),
            ('swift-storage', parsed_args.swift_storage_flavor,
                parsed_args.swift_storage_scale),
        ):
            if flavor is None or scale == 0:
                self.log.debug("--{}-flavor not used".format(target))
            elif flavor not in flavors:
                self.predeploy_errors += 1
                self.log.error(message.format(target, flavor))