Fix the `Gitlab::Seeder` monkey patch to disable mail delivery

db/fixtures/development/13_comments.rb

 require './spec/support/sidekiq'
 
 Gitlab::Seeder.quiet do
-  Issue.all.each do |issue|
+  Issue.find_each do |issue|
     project = issue.project
 
     project.team.users.each do |user|
@@ -16,7 +16,7 @@ Gitlab::Seeder.quiet do
     end
   end
 
-  MergeRequest.all.each do |mr|
+  MergeRequest.find_each do |mr|
     project = mr.project
 
     project.team.users.each do |user|

lib/gitlab/seeder.rb

+module DeliverNever
+  def deliver_later
+    self
+  end
+end
+
 module Gitlab
   class Seeder
     def self.quiet
       mute_mailer
       SeedFu.quiet = true
+
       yield
+
       SeedFu.quiet = false
       puts "\nOK".color(:green)
     end
 
-    def self.by_user(user)
-      yield
-    end
-
     def self.mute_mailer
-      code = <<-eos
-def Notify.deliver_later
-  self
-end
-      eos
-      eval(code) # rubocop:disable Security/Eval
+      ActionMailer::MessageDelivery.prepend(DeliverNever)
     end
   end
 end