Ruby on Rails

Thank you Jason for your fast reply. I didn't know about the default
logger, I have changed my code. Yes it is in a controller, in the create
action: https://gist.github.com/anonymous/d138a4f2c76bb4b32dd2

The full log:
Started POST "/game" for 127.0.0.1 at 2014-09-03 00:14:49 +0200
Processing by GameController#create as HTML
  Parameters: {"utf8"=>"V",
"authenticity_token"=>"gx7TovN+tZbMxOTc91l5P/5jqviBx
eO9vlJQaxJ19No=", "game"=>{"small_blind"=>"1", "big_blind"=>"2",
"player_number"
=>"2"}, "commit"=>"New game !"}
cards
#<ActiveRecord::Associations::CollectionProxy::ActiveRecord_Associations_Collect
ionProxy_Card:0x3b762e8>
0
players
Completed 500 Internal Server Error in 114ms

SyntaxError
(C:/site/app/models/player.rb:48: voi
d value expression):
  app/controllers/game_controller.rb:11:in `create'