Failure when trying to start Spree Commerce, using Unicorn, with RBX

gistfile1.txt

E, [2014-09-29T11:41:02.514948 #14103] ERROR -- : Error trying to compile /usr/local/rvm/gems/rbx-2.2.10/gems/rack-1.5.2/lib/rack/builder.rb (Rubinius::ToolSets::Runtime::CompileError)
/usr/local/rvm/rubies/rbx-2.2.10/runtime/gems/rubinius-compiler-2.1.1/lib/rubinius/compiler/compiler.rbc:13:in `compiler_error'
/usr/local/rvm/rubies/rbx-2.2.10/runtime/gems/rubinius-compiler-2.1.1/lib/rubinius/compiler/compiler.rbc:95:in `compile'
kernel/delta/code_loader.rb:217:in `compile_file'
kernel/delta/code_loader.rb:190:in `load_file'
kernel/common/code_loader.rb:128:in `require'
kernel/common/code_loader.rb:237:in `require'
kernel/common/autoload.rb:55:in `resolve'
config.ru:1:in `__script__'
kernel/common/block_environment.rb:53:in `call_on_instance'
kernel/common/eval.rb:176:in `eval'
/usr/local/rvm/gems/rbx-2.2.10/gems/unicorn-4.8.3/lib/unicorn.rb:48:in `builder'
kernel/bootstrap/proc.rb:20:in `call'
/usr/local/rvm/gems/rbx-2.2.10/gems/unicorn-4.8.3/lib/unicorn/http_server.rb:764:in `build_app!'
/usr/local/rvm/gems/rbx-2.2.10/gems/unicorn-4.8.3/lib/unicorn/http_server.rb:628:in `init_worker_process'
/usr/local/rvm/gems/rbx-2.2.10/gems/unicorn-4.8.3/lib/unicorn/http_server.rb:651:in `worker_loop'
/usr/local/rvm/gems/rbx-2.2.10/gems/unicorn-4.8.3/lib/unicorn/http_server.rb:525:in `spawn_missing_workers'
/usr/local/rvm/gems/rbx-2.2.10/gems/unicorn-4.8.3/lib/unicorn/http_server.rb:140:in `start'
/usr/local/rvm/gems/rbx-2.2.10/gems/unicorn-4.8.3/bin/unicorn:126:in `__script__'
kernel/common/kernel.rb:447:in `load'
/usr/local/rvm/gems/rbx-2.2.10/bin/unicorn:23:in `__script__'
kernel/common/block_environment.rb:53:in `call_on_instance'
kernel/common/eval.rb:176:in `eval'
/usr/local/rvm/gems/ruby-2.0.0-p353/bin/ruby_executable_hooks:15:in `__script__'
kernel/delta/code_loader.rb:66:in `load_script'
kernel/delta/code_loader.rb:152:in `load_script'
kernel/loader.rb:649:in `script'
kernel/loader.rb:825:in `main'