Make migration pseudo-reversible

db/migrate/20180222145909_fix_timestamps_on_feedback.rb

@@ -1,6 +1,10 @@
 class FixTimestampsOnFeedback < ActiveRecord::Migration
-  def change
+  def up
     change_column_default(:user_exercise_feedbacks, :created_at, nil)
     change_column_default(:user_exercise_feedbacks, :updated_at, nil)
   end
+
+  def down
+    
+  end
 end