Clean up check_channel_announcement style

`check_channel_announcement` had long lines, a (very-)stale TODO
and confusing variable assignment, which is all cleaned up here.

Author: TheBlueMatt

lightning/src/routing/gossip_checking.rs

@@ -37,31 +37,39 @@ pub trait ChainAccess {
 pub(crate) fn check_channel_announcement<A: Deref>(
 	chain_access: &Option<A>, msg: &msgs::UnsignedChannelAnnouncement
 ) -> Result<Option<u64>, msgs::LightningError> where A::Target: ChainAccess {
-	let utxo_value = match chain_access {
+	match chain_access {
 		&None => {
 			// Tentatively accept, potentially exposing us to DoS attacks
-			None
+			Ok(None)
 		},
 		&Some(ref chain_access) => {
 			match chain_access.get_utxo(&msg.chain_hash, msg.short_channel_id) {
 				Ok(TxOut { value, script_pubkey }) => {
 					let expected_script =
 						make_funding_redeemscript(&msg.bitcoin_key_1, &msg.bitcoin_key_2).to_v0_p2wsh();
 					if script_pubkey != expected_script {
-						return Err(LightningError{err: format!("Channel announcement key ({}) didn't match on-chain script ({})", expected_script.to_hex(), script_pubkey.to_hex()), action: ErrorAction::IgnoreError});
+						return Err(LightningError{
+							err: format!("Channel announcement key ({}) didn't match on-chain script ({})",
+								expected_script.to_hex(), script_pubkey.to_hex()),
+							action: ErrorAction::IgnoreError
+						});
 					}
-					//TODO: Check if value is worth storing, use it to inform routing, and compare it
-					//to the new HTLC max field in channel_update
-					Some(value)
+					Ok(Some(value))
 				},
 				Err(ChainAccessError::UnknownChain) => {
-					return Err(LightningError{err: format!("Channel announced on an unknown chain ({})", msg.chain_hash.encode().to_hex()), action: ErrorAction::IgnoreError});
+					Err(LightningError {
+						err: format!("Channel announced on an unknown chain ({})",
+							msg.chain_hash.encode().to_hex()),
+						action: ErrorAction::IgnoreError
+					})
 				},
 				Err(ChainAccessError::UnknownTx) => {
-					return Err(LightningError{err: "Channel announced without corresponding UTXO entry".to_owned(), action: ErrorAction::IgnoreError});
+					Err(LightningError {
+						err: "Channel announced without corresponding UTXO entry".to_owned(),
+						action: ErrorAction::IgnoreError
+					})
 				},
 			}
 		}
-	};
-	Ok(utxo_value)
+	}
 }