Installing CDH 5.1 using CM 5.1.1. During the Cluster Setup, Starting Sark Service failed. After clicking Details, 4 child commands failed including 2 for starting this worker, 1 for starting this history server, and 1 for starting this master. In the stderr, it shows "startng spark worker using spark://hostname:7077" and then "SCALA_HOME is not set". Please help.