Fallback to ::Logger if Rails::Logger not loaded (#3)

Some rake tasks do not load the environment, and so ::Rails::Logger is nil. In those cases, we fallback to ::Logger.new(STDOUT)

lib/rails-callback_log.rb

@@ -9,6 +9,10 @@ module RailsCallbackLog
   FILTER = ENV["RAILS_CALLBACK_LOG_FILTER"].present?.freeze
 
   class << self
+    def logger
+      ::Rails.logger || ::Logger.new(STDOUT)
+    end
+
     def matches_filter?(str)
       source_location_filters.any? { |f| str.start_with?(f) }
     end
@@ -28,7 +32,7 @@ def make_lambda
       lambda { |*args, &block|
         if !::RailsCallbackLog::FILTER ||
           caller.any? { |line| ::RailsCallbackLog.matches_filter?(line) }
-          ::Rails.logger.debug(format("Callback: %s", @method_name))
+          ::RailsCallbackLog.logger.debug(format("Callback: %s", @method_name))
         end
         original_lambda.call(*args, &block)
       }
@@ -43,7 +47,7 @@ def make_lambda(filter)
       lambda { |*args, &block|
         if !::RailsCallbackLog::FILTER ||
           caller.any? { |line| ::RailsCallbackLog.matches_filter?(line) }
-          ::Rails.logger.debug(format("Callback: %s", filter))
+          ::RailsCallbackLog.logger.debug(format("Callback: %s", filter))
         end
         original_lambda.call(*args, &block)
       }

spec/rails-callback_log_spec.rb

@@ -16,7 +16,7 @@ module Callbacks
             # Mock the rails logger. We're going to expect it to receive a `debug` message.
             logger = double
             allow(logger).to receive(:debug)
-            allow(::Rails).to receive(:logger).and_return(logger)
+            allow(::RailsCallbackLog).to receive(:logger).and_return(logger)
             target = double
 
             # Symbol-based callbacks have a `target` and a `value`. The definition of