Trying to run Foreman when ruby_parser 2.0.6 is installed fails with the following error:

/usr/share/foreman/app/models/environment.rb:1: superclass mismatch for class Environment (TypeError)

This is caused by this versions ruby_parser defining Environment constant itself. With version 2.3.1 this is not the case.

It means Foreman is dependent on this or higher version being installed and therefore it should be added to Gemfile (patch attached), and also into RPMS and DEBS explicitly.