Ancestry 2.1.0 dropped Ruby 1.8 support
develop is currently failing due to Ancestry 2.1.0 using some Ruby 1.9-isms.
undefined method `require_relative' for main:Object
It should be pinned, at least temporarily.
fixes #5214 - pin ancestry for Ruby 1.8 compatibility
(cherry picked from commit 18e392f2eb6f568d0291d0037a3a87caf050ca5a)