Replace error-chain for client error (#2231)

* WIP: convert client error

* Remove error_chain for client error

* Ignore tx-pool error deprecation warning

* Update Cargo.lock files

* Fix tests

* Increment impl_version

* Derive From impls, remove allow(missing_docs)

* Remove space

* Remove redundant into()s

* Blockchain Error source

* Bump impl version

substrate/core/consensus/aura/slots/src/lib.rs

@@ -226,7 +226,7 @@ impl SlotDuration {
 		match client.get_aux(SLOT_KEY)? {
 			Some(v) => u64::decode(&mut &v[..])
 				.map(SlotDuration)
-				.ok_or_else(|| ::client::error::ErrorKind::Backend(
+				.ok_or_else(|| ::client::error::Error::Backend(
 					format!("Aura slot duration kept in invalid format"),
 				).into()),
 			None => {