Seed is not seed dump.

lib/tasks/seed.rake

 namespace :db do
-  namespace :seed  do
-    desc "Seed is replaced with seed_fu"
-    task :dump => :environment do
-      raise "Please run db:seed_fu instead of db:seed."
-    end
+  desc "Seed is replaced with seed_fu"
+  task :seed => :environment do
+    raise "Please run db:seed_fu instead of db:seed."
   end
 end