Expunge error-chain (feat. tomaka) (#2662)

* Remove error_chain

* Expunge error-chain from rpc and service.

* Expunge from transaction pool.

* Expunge from node/cli

* Expunge from keystore.

* Remove some boilerplate.

* Fix remaining stuff.

* Improve on deprecation message.

* Fix issues.

* Fix trnsaction pool tests.

* Fix the rest.

* Fix borked merge.

* Update lock

substrate/core/service/src/error.rs

@@ -16,32 +16,49 @@
 
 //! Errors that can occur during the service operation.
 
-// Silence: `use of deprecated item 'std::error::Error::cause': replaced by Error::source, which can support downcasting`
-// https://github.com/paritytech/substrate/issues/1547
-#![allow(deprecated)]
-
 use client;
 use network;
 use keystore;
 use consensus_common;
-use error_chain::*;
 
-error_chain! {
-	foreign_links {
-		Client(client::error::Error) #[doc="Client error"];
-		Io(::std::io::Error) #[doc="IO error"];
+/// Service Result typedef.
+pub type Result<T> = std::result::Result<T, Error>;
+
+/// Service errors.
+#[derive(Debug, derive_more::Display, derive_more::From)]
+pub enum Error {
+	/// Client error.
+	Client(client::error::Error),
+	/// IO error.
+	Io(std::io::Error),
+	/// Consensus error.
+	Consensus(consensus_common::Error),
+	/// Network error.
+	Network(network::error::Error),
+	/// Keystore error.
+	Keystore(keystore::Error),
+	/// Best chain selection strategy is missing.
+	#[display(fmt="Best chain selection strategy (SelectChain) is not provided.")]
+	SelectChainRequired,
+	/// Other error.
+	Other(String),
+}
+
+impl<'a> From<&'a str> for Error {
+	fn from(s: &'a str) -> Self {
+		Error::Other(s.into())
 	}
+}
 
-	links {
-		Consensus(consensus_common::Error, consensus_common::ErrorKind) #[doc="Consensus error"];
-		Network(network::error::Error, network::error::ErrorKind) #[doc="Network error"];
-		Keystore(keystore::Error, keystore::ErrorKind) #[doc="Keystore error"];
-	}
-
-	errors {
-		SelectChainRequired {
-			description("Best chain selection strategy (SelectChain) must be provided when starting full node or authority."),
-			display("Best chain selection strategy (SelectChain) is not provided."),
+impl std::error::Error for Error {
+	fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+		match self {
+			Error::Client(ref err) => Some(err),
+			Error::Io(ref err) => Some(err),
+			Error::Consensus(ref err) => Some(err),
+			Error::Network(ref err) => Some(err),
+			Error::Keystore(ref err) => Some(err),
+			_ => None,
 		}
 	}
 }