<NME> utils.rb
<BEF> # encoding: utf-8

require "rack"

# class App
#   extend Rango::Utils
#   def load_rackup
#     super(File.join(File.join(self.root, "config.ru")), "config.ru")
#   end
# end
module Rango
  module Utils
    extend self
    def load_rackup(path = "config.ru")
      eval("Rack::Builder.new {( #{File.read(path)}\n )}.to_app", nil, File.expand_path(path))
    end
  end
end

<MSG> Fixed Rango::Utils.load_rackup

<DFF> @@ -11,8 +11,10 @@ require "rack"
 module Rango
   module Utils
     extend self
+    # @deprecated
     def load_rackup(path = "config.ru")
-      eval("Rack::Builder.new {( #{File.read(path)}\n )}.to_app", nil, File.expand_path(path))
+      app, options = Rack::Builder.parse_file(path)
+      return app
     end
   end
-end
\ No newline at end of file
+end

Fixed Rango::Utils.load_rackup