Version of xenomai is marked for autoremoval from testing on Thu 15 Jun 2017. It depends (transitively) on kernel-package, affected by 848066, 849357, 856322. You should try to prevent the removal by fixing these RC bugs.
This package has been
orphaned. This means that it does not have a real
maintainer at the moment. Please consider adopting this package
if you are interested in it. Please see bug number #813470 for more information.