Backport relevant changes from EE https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/4827 to CE

app/models/project_team.rb

@@ -85,6 +85,15 @@ class ProjectTeam
     @masters ||= fetch_members(Gitlab::Access::MASTER)
   end
+  def owners
+    @owners ||=
+      if group
+        group.owners
+      else
+        [project.owner]
+      end
+  end
+
   def import(source_project, current_user = nil)
     target_project = project

app/services/users/destroy_service.rb

@@ -49,6 +49,8 @@ module Users
         ::Projects::DestroyService.new(project, current_user, skip_repo: project.legacy_storage?).execute
       end
+      yield(user) if block_given?
+
       MigrateToGhostUserService.new(user).execute unless options[:hard_delete]
       # Destroy the namespace after destroying the user since certain methods may depend on the namespace existing