confirmation: biomaj-watcher has been compiled with jdk8 on upgrades, if jdk7 is installed, it will fail to execute/install
in case of upgrade, we switch from jdk7 to jdk8, but install is first made against jdk7. jdk must be upgraded first, then biomaj-watcher can be installed. Solution would be to compile (d/rules) WatcherConfigurator and UpdateToBiomaj java files with source and target options to 1.5. No impact on stretch directly as default is jdk 1.8. A patch could be done on jessie-backports to fix the upgrade issue, but backports need to be set in apt sources....
