make logger a singleton on the class

activesupport/lib/active_support/log_subscriber.rb

@@ -48,14 +48,14 @@ module ActiveSupport
     mattr_accessor :colorize_logging
     self.colorize_logging = true
 
-    class_attribute :logger
-
     class << self
-      remove_method :logger
       def logger
         @logger ||= Rails.logger if defined?(Rails)
+        @logger
       end
 
+      attr_writer :logger
+
       def attach_to(namespace, log_subscriber=new, notifier=ActiveSupport::Notifications)
         log_subscribers << log_subscriber
         @@flushable_loggers = nil
@@ -91,6 +91,10 @@ module ActiveSupport
       super
     end
 
+    def logger
+      LogSubscriber.logger
+    end
+
     def start(name, id, payload)
       return unless logger