rails--rails/activesupport/lib/active_support/logger.rb

require 'logger'

module ActiveSupport
  class Logger < ::Logger
    def initialize(*args)
      super
      @formatter = SimpleFormatter.new
    end

    # Simple formatter which only displays the message.
    class SimpleFormatter < ::Logger::Formatter
      # This method is invoked when a log event occurs
      def call(severity, timestamp, progname, msg)
        "#{String === msg ? msg : msg.inspect}\n"
      end
    end
  end
end