code: def _check_flavors_exist(self, parsed_args):
          
          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))
docs: Ensure that selected flavors (--ROLE-flavor) exist in nova.