sdformat 4.1.0-1 is marked for autoremoval from testing on 2016-10-04
It is affected by these RC bugs:
834982: sdformat: FTBFS in testing ('_link' has incomplete type)-- debian-science-maintainers mailing list debian-science-maintainers@lists.alioth.debian.org http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/debian-science-maintainers
