Add temporary logging to the merge train refresh service

MR: gitlab.com/gitlab-org/gitlab/-/merge_requests/179372

ee/app/services/merge_trains/refresh_merge_request_service.rb

@@ -16,6 +16,9 @@ def execute(merge_request)
 
       validate!
       pipeline_created = create_pipeline! if merge_train_car.requires_new_pipeline? || require_recreate?
+
+      log_running_security_scans
+
       merge! if merge_train_car.mergeable?
 
       success(pipeline_created: pipeline_created.present?)
@@ -166,5 +169,9 @@ def abort(error)
 
       error(error.message)
     end
+
+    def log_running_security_scans
+      Gitlab::AppLogger.warn("Security scans running") if merge_request.running_scan_result_policy_violations.any?
+    end
   end
 end

ee/spec/services/merge_trains/refresh_merge_request_service_spec.rb

@@ -296,8 +296,40 @@
       end
 
       context 'when the merge request is the first queue' do
+        let(:policy) { create(:scan_result_policy_read, project: project) }
+
         it_behaves_like 'merges the merge request'
 
+        context 'when a security scan is running' do
+          before do
+            create(:scan_result_policy_violation, :running, project: project, merge_request: merge_request,
+              scan_result_policy_read: policy, violation_data: nil)
+          end
+
+          it 'logs that the scan is running' do
+            project.update!(merge_method: :ff)
+            project.repository.raw_repository.write_ref(merge_request.train_ref_path, pipeline.sha)
+            expect(Gitlab::AppLogger).to receive(:warn).with("Security scans running")
+
+            subject
+          end
+        end
+
+        context 'when no scan is running' do
+          before do
+            create(:scan_result_policy_violation, :warn, project: project, merge_request: merge_request,
+              scan_result_policy_read: policy, violation_data: nil)
+          end
+
+          it 'does not log' do
+            project.update!(merge_method: :ff)
+            project.repository.raw_repository.write_ref(merge_request.train_ref_path, pipeline.sha)
+            expect(Gitlab::AppLogger).not_to receive(:warn)
+
+            subject
+          end
+        end
+
         using RSpec::Parameterized::TableSyntax
 
         where(:merge_method) do