[DRE-maint] ruby-sprite-factory is marked for autoremoval from testing

[Debian testing autoremoval watch]

ruby-sprite-factory 1.7.1-2 is marked for autoremoval from testing on 2017-01-01

It (build-)depends on packages with these RC bugs:
591419: ruby-rmagick: librmagick-ruby should not be installable with imagemagick