introduce errors with info (#1834)

polkadot/node/core/candidate-validation/src/lib.rs

@@ -20,8 +20,11 @@
 //! according to a validation function. This delegates validation to an underlying
 //! pool of processes used for execution of the Wasm.
 
+#![deny(unused_crate_dependencies, unused_results)]
+#![warn(missing_docs)]
+
 use polkadot_subsystem::{
-	Subsystem, SubsystemContext, SpawnedSubsystem, SubsystemResult,
+	Subsystem, SubsystemContext, SpawnedSubsystem, SubsystemResult, SubsystemError,
 	FromOverseer, OverseerSignal,
 	messages::{
 		AllMessages, CandidateValidationMessage, RuntimeApiMessage,
@@ -116,9 +119,13 @@ impl<S, C> Subsystem<C> for CandidateValidationSubsystem<S> where
 	S: SpawnNamed + Clone + 'static,
 {
 	fn start(self, ctx: C) -> SpawnedSubsystem {
+		let future = run(ctx, self.spawn, self.metrics)
+			.map_err(|e| SubsystemError::with_origin("candidate-validation", e))
+			.map(|_| ())
+			.boxed();
 		SpawnedSubsystem {
 			name: "candidate-validation-subsystem",
-			future: run(ctx, self.spawn, self.metrics).map(|_| ()).boxed(),
+			future,
 		}
 	}
 }