Log signing message type during attempted double sign events

It seems possible the KMS might be rejecting some potentially valid
`<nil>` PreCommits, however it's difficult to ascertain right now as
this information isn't presently logged as part of the double signing
error message.

This adds additional logging (and also extracts the double signing
handler into its own function)

src/session.rs

@@ -131,19 +131,10 @@ impl Session {
             if let Err(e) = chain_state.update_consensus_state(request_state.clone()) {
                 // Report double signing error back to the validator
                 if e.kind() == StateErrorKind::DoubleSign {
-                    let height = request.height().unwrap();
-
-                    error!(
-                        "[{}:{}] attempted double sign at h/r/s: {} ({} != {})",
-                        &self.config.chain_id,
-                        &self.config.addr,
-                        request_state,
-                        chain_state.consensus_state().block_id_prefix(),
-                        request_state.block_id_prefix()
+                    return self.handle_double_signing(
+                        request,
+                        &chain_state.consensus_state().block_id_prefix(),
                     );
-
-                    let remote_err = RemoteError::double_sign(height);
-                    return Ok(request.build_response(Some(remote_err)));
                 } else {
                     return Err(e.into());
                 }
@@ -214,4 +205,31 @@ impl Session {
             started_at.elapsed().as_millis(),
         );
     }
+
+    /// Handle attempted double signing
+    fn handle_double_signing<T: TendermintRequest + Debug>(
+        &self,
+        request: T,
+        original_block_id: &str,
+    ) -> Result<Response, Error> {
+        let msg_type = request
+            .msg_type()
+            .map(|t| format!("{:?}", t))
+            .unwrap_or_else(|| "Unknown".to_owned());
+
+        let request_state = request.consensus_state().unwrap();
+
+        error!(
+            "[{}:{}] attempted double sign for {} at h/r/s: {} ({} != {})",
+            &self.config.chain_id,
+            &self.config.addr,
+            msg_type,
+            request_state,
+            original_block_id,
+            request_state.block_id_prefix()
+        );
+
+        let remote_err = RemoteError::double_sign(request.height().unwrap());
+        return Ok(request.build_response(Some(remote_err)));
+    }
 }