fix(tools): better alert messaging (#54383)

Co-authored-by: Ben Zhang <bz2065@nyu.edu>

tools/challenge-editor/client/src/utils/handle-request.ts

@@ -1,7 +1,20 @@
 export const handleRequest = (makeRequest: () => Promise<Response>) => () => {
   makeRequest()
-    .then(res => res.json() as Promise<{ stdout: string; stderr: string }>)
-    .then(data => alert(JSON.stringify(data)))
+    .then(
+      res =>
+        res.json() as Promise<{
+          stdout?: string;
+          stderr?: string;
+          message?: string;
+        }>
+    )
+    .then(data => {
+      if (data.message) {
+        alert(data.message);
+      } else {
+        alert(JSON.stringify(data));
+      }
+    })
     .catch(err => console.error(err));
 };