def trim_unreachable_packages(workspace, soln_constraints)
      reachable_packages = []
      soln_constraints.each do |soln_constraint|
        find_reachable_packages(workspace,
                                soln_constraint.package,
                                soln_constraint.constraint,
                                reachable_packages)
      end

      reachable_packages
    end
def trim_unreachable_packages(workspace, soln_constraints)
      reachable_packages = []
      soln_constraints.each do |soln_constraint|
        find_reachable_packages(workspace,
                                soln_constraint.package,
                                soln_constraint.constraint,
                                reachable_packages)
      end

      reachable_packages
    end
Given a workspace and solution constraints, this method returns
 an array that includes only packages that can be induced by the
 solution constraints.