Github user zentol commented on the issue:
https://github.com/apache/flink/pull/5118
`flink-core` is a direct dependency due to the usage of the
[Collector](https://github.com/apache/flink/blob/master/flink-quickstart/flink-quickstart-java/src/main/resources/archetype-resources/src/main/java/WordCount.java)
class which is part of flink-core.---
