Unify error enums in substrate and ethereum clients with thiserror (#1094)

* Unify error enums in substrate and ethereum clients with `thiserror`

Related to https://github.com/paritytech/parity-bridges-common/issues/857

* Add license pre-amble

* rustfmt

* Fix spelling

bridges/relays/messages/Cargo.toml

@@ -6,7 +6,6 @@ edition = "2018"
 license = "GPL-3.0-or-later WITH Classpath-exception-2.0"
 
 [dependencies]
-anyhow = "1.0"
 async-std = { version = "1.6.5", features = ["attributes"] }
 async-trait = "0.1.40"
 futures = "0.3.5"

bridges/relays/messages/src/message_lane_loop.rs

@@ -263,7 +263,7 @@ pub async fn run<P: MessageLane>(
 	target_client: impl TargetClient<P>,
 	metrics_params: MetricsParams,
 	exit_signal: impl Future<Output = ()> + Send + 'static,
-) -> anyhow::Result<()> {
+) -> Result<(), relay_utils::Error> {
 	let exit_signal = exit_signal.shared();
 	relay_utils::relay_loop(source_client, target_client)
 		.reconnect_delay(params.reconnect_delay)