At this point, with Hadoop 3 on deck, I think hadoop 2.6 is both fairly old, and actually, not different from 2.7 with respect to Spark. That is, I don't know if we are actually maintaining anything here but a separate profile and 2x the number of test builds.
The cost is, by the same token, low. However I'm floating the idea of removing the 2.6 profile and just requiring 2.7+ as of Spark 2.4?
