rpc-api: use thiserror instead of derive_more for error handling (#9631)

Signed-off-by: koushiro <koushiro.cqx@gmail.com>

substrate/client/rpc-api/src/chain/error.rs

@@ -28,24 +28,16 @@ pub type Result<T> = std::result::Result<T, Error>;
 pub type FutureResult<T> = jsonrpc_core::BoxFuture<Result<T>>;
 
 /// Chain RPC errors.
-#[derive(Debug, derive_more::Display, derive_more::From)]
+#[derive(Debug, thiserror::Error)]
 pub enum Error {
 	/// Client error.
-	#[display(fmt = "Client error: {}", _0)]
-	Client(Box<dyn std::error::Error + Send>),
+	#[error("Client error: {}", .0)]
+	Client(#[from] Box<dyn std::error::Error + Send>),
 	/// Other error type.
+	#[error("{0}")]
 	Other(String),
 }
 
-impl std::error::Error for Error {
-	fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
-		match self {
-			Error::Client(ref err) => Some(&**err),
-			_ => None,
-		}
-	}
-}
-
 /// Base error code for all chain errors.
 const BASE_ERROR: i64 = 3000;