private Collection<Partition> getPartitions(final String topicName) {
		return getPartitions(topicName, 0);
	}
Fetches partition data, throwing an exception if the expected number is not met after a number of
subsequent retries
@param topicName topic
@param expectedNumber expected number of partitions. If less or equal to 0, check is suppressed.
@return the partitions
spring-xd-messagebus-kafka/src/main/java/org/springframework/xd/dirt/integration/kafka/KafkaMessageBus.java