Fix pallet_migrations benchmark when FailedMigrationHandler emits events (#8694)

When FailedMigrationHandler emits events, the `UpgradeFailed` event is
not the last one, so `assert_last_event` fails. Fixed by checking that
the `UpgradeFailed` event is emitted, even if it is not the last one.

---------

Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Bastian Köcher <git@kchr.de>

Author: 3 people

prdoc/pr_8694.prdoc

@@ -0,0 +1,9 @@
+title: Fix pallet_migrations benchmark when FailedMigrationHandler emits events
+doc:
+- audience: Runtime Dev
+  description: When FailedMigrationHandler emits events, the `UpgradeFailed` event
+    is not the last one, so `assert_last_event` fails. Fixed by checking that the
+    `UpgradeFailed` event is emitted, even if it is not the last one.
+crates:
+- name: pallet-migrations
+  bump: patch

substrate/frame/migrations/src/benchmarking.rs

@@ -26,6 +26,10 @@ use sp_core::{twox_128, Get};
 use sp_io::{storage, KillStorageResult};
 use sp_runtime::traits::One;
 
+fn assert_has_event<T: Config>(generic_event: <T as Config>::RuntimeEvent) {
+	frame_system::Pallet::<T>::assert_has_event(generic_event.into());
+}
+
 fn assert_last_event<T: Config>(generic_event: <T as Config>::RuntimeEvent) {
 	frame_system::Pallet::<T>::assert_last_event(generic_event.into());
 }
@@ -152,7 +156,7 @@ mod benches {
 			Pallet::<T>::exec_migration(c, false, &mut meter);
 		}
 
-		assert_last_event::<T>(Event::UpgradeFailed {}.into());
+		assert_has_event::<T>(Event::UpgradeFailed {}.into());
 
 		Ok(())
 	}