Clarify Pantsd error message wording

# Building wheels and fs_util will be skipped. Delete if not intended.
[ci skip-build-wheels]

src/rust/engine/nailgun/src/client.rs

@@ -143,10 +143,7 @@ pub async fn client_execute(
   let socket = TcpStream::connect((Ipv4Addr::new(127, 0, 0, 1), port))
     .await
     .map_err(|err| {
-      NailgunClientError::PreConnect(format!(
-        "Nailgun client error connecting to localhost: {}",
-        err
-      ))
+      NailgunClientError::PreConnect(format!("Failed to connect to localhost: {}", err))
     })?;
 
   let mut child = nails::client::handle_connection(config, socket, command, async {
@@ -155,7 +152,7 @@ pub async fn client_execute(
     stdin_read
   })
   .await
-  .map_err(|err| NailgunClientError::PreConnect(format!("Failed to start remote task: {}", err)))?;
+  .map_err(|err| NailgunClientError::PreConnect(format!("Failed to start: {}", err)))?;
 
   handle_client_output(
     child.output_stream.take().unwrap(),
@@ -167,7 +164,7 @@ pub async fn client_execute(
   let exit_code: ExitCode = child
     .wait()
     .await
-    .map_err(|err| NailgunClientError::PostConnect(format!("Nailgun client error: {}", err)))?;
+    .map_err(|err| NailgunClientError::PostConnect(format!("Failed during execution: {}", err)))?;
 
   Ok(exit_code.0)
 }

src/rust/engine/src/externs/interface.rs

@@ -702,7 +702,7 @@ py_class!(class PyNailgunClient |py| {
       )).map(|code| code.to_py_object(py)).map_err(|e| match e{
         NailgunClientError::PreConnect(err_str) => PyErr::new::<NailgunConnectionException, _>(py, (err_str,)),
         NailgunClientError::PostConnect(s) => {
-          let err_str = format!("Nailgun client error: {:?}", s);
+          let err_str = format!("Pantsd client error: {}", s);
           PyErr::new::<NailgunClientException, _>(py, (err_str,))
         },
         NailgunClientError::BrokenPipe => {