* version/2.5:
  Report the command that is failing
  update rtd_upgrade.sh and xhive in response to readthedocs stable build image update
  add a section regarding install requirements for guest languages
  The Docker image needs jdk12 too
  Not needed
  jdk13 is early access (not even release candidate). We should stick to a released version, e.g. jdk12
  We moved away from Oracle
  [docker] Cleanup the cpan working directory too to make the layer (slightly) smaller
  wrappers/java/pom.xml: bump jackson-databind to 2.9.9
  Fix travis build
  Java wrapper moved to open JDK
  Version of mvn changed to proj version
  Version changes, added CompileJava module run.
  Set of minimal dependencies
  Java build with maven
  bugfix: oracle-java8 is not available any more, but openjdk-8 works