fix warning about postfixOps which creates this output with -feature:
[warn] by making the implicit value scala.language.postfixOps visible.
[warn] This can be achieved by adding the import clause 'import scala.language.postfixOps'
[warn] or by setting the compiler option -language:postfixOps.
[warn] See the Scala docs for value scala.language.postfixOps for a discussion
[warn] why the feature should be explicitly enabled.
[warn] val stdout = "dcos task --completed" !!
[warn] ^
[warn] /home/stavros/workspace/dev/spark-it/evaluate_prs/mesos-spark-integration-tests/test-runner/src/main/scala/com/typesafe/spark/test/mesos/framework/runners/DCOSUtils.scala:25: postfix operator !! should be enabled
[warn] by making the implicit value scala.language.postfixOps visible.
[warn] cmd !!
[warn] ^
[warn] /home/stavros/workspace/dev/spark-it/evaluate_prs/mesos-spark-integration-tests/test-runner/src/main/scala/com/typesafe/spark/test/mesos/framework/runners/DCOSUtils.scala:42: postfix operator !! should be enabled
[warn] by making the implicit value scala.language.postfixOps visible.
[warn] val output = proc !!
[warn] ^
[warn] three warnings found
[warn] by making the implicit value scala.language.postfixOps visible. [warn] This can be achieved by adding the import clause 'import scala.language.postfixOps' [warn] or by setting the compiler option -language:postfixOps. [warn] See the Scala docs for value scala.language.postfixOps for a discussion [warn] why the feature should be explicitly enabled. [warn] val stdout = "dcos task --completed" !! [warn] ^ [warn] /home/stavros/workspace/dev/spark-it/evaluate_prs/mesos-spark-integration-tests/test-runner/src/main/scala/com/typesafe/spark/test/mesos/framework/runners/DCOSUtils.scala:25: postfix operator !! should be enabled [warn] by making the implicit value scala.language.postfixOps visible. [warn] cmd !! [warn] ^ [warn] /home/stavros/workspace/dev/spark-it/evaluate_prs/mesos-spark-integration-tests/test-runner/src/main/scala/com/typesafe/spark/test/mesos/framework/runners/DCOSUtils.scala:42: postfix operator !! should be enabled [warn] by making the implicit value scala.language.postfixOps visible. [warn] val output = proc !! [warn] ^ [warn] three warnings found