Sends a notification to mirror_user when mirror hard fails

app/mailers/emails/projects.rb

@@ -38,5 +38,13 @@ module Emails
            reply_to:  @message.reply_to,
            subject:   @message.subject)
     end
+
+    def mirror_hard_failed(project_id, user_id)
+      @current_user = @user = User.find user_id
+      @project = Project.find project_id
+
+      mail(to: @user.notification_email,
+           subject: subject('Mirror hard failed'))
+    end
   end
 end

ee/app/models/ee/project/import_status_state_machine.rb

@@ -21,7 +21,10 @@ module EE
           end
 
           after_transition [:scheduled, :started] => [:finished, :failed] do |project, _|
-            ::Gitlab::Mirror.decrement_capacity(project.id) if project.mirror?
+            if project.mirror?
+              ::Gitlab::Mirror.decrement_capacity(project.id)
+              ::NotificationService.new.mirror_was_hard_failed(project)
+            end
           end
 
           before_transition started: :failed do |project, _|

ee/app/services/ee/notification_service.rb

@@ -22,5 +22,11 @@ module EE
 
       Notify.service_desk_new_note_email(issue.id, note.id).deliver_later
     end
+
+    def mirror_was_hard_failed(project)
+      recepient = project.mirror_user
+
+      mailer.mirror_hard_failed(project.id, recepient.id).deliver_later
+    end
   end
 end