private Map<TopicPartition, Errors> partitionErrors(Collection<TopicPartition> partitions, Errors error) {
        final Map<TopicPartition, Errors> errors = new HashMap<>();
        for (TopicPartition partition : partitions) {
            errors.put(partition, error);
        }
        return errors;
    }
Verifies that subscription change updates SubscriptionState correctly even after JoinGroup failures
that don't re-invoke onJoinPrepare.
clients/src/test/java/org/apache/kafka/clients/consumer/internals/ConsumerCoordinatorTest.java