[stable2409] Backport #8694 (#9028)

Backport #8694 into `stable2409` from tmpolaczyk.

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[documentation](https://github.com/paritytech/polkadot-sdk/blob/master/docs/BACKPORT.md)
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Co-authored-by: tmpolaczyk <[email protected]>
Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Bastian Köcher <[email protected]>

Author: 4 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

@@ -23,6 +23,10 @@ use frame_benchmarking::{v2::*, BenchmarkError};
 use frame_system::{Pallet as System, RawOrigin};
 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());
 }
@@ -149,7 +153,7 @@ 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(())
 	}