Handle request errors

assets/js/contact_form.js

@@ -16,10 +16,19 @@ window.addEventListener('DOMContentLoaded', function(event) {
         mode: 'same-origin',
         body: formData,
     })
-    .then(response => response.json())
+    .then(response => {
+        if (!response.ok) {
+            throw new Error('Response was not OK');
+        }
+
+        return response.json();
+    })
     .then(json => {
         console.log(json);
     })
+    .catch(error => {
+        console.error('Could not start the session:', error);
+    });
 });
 
 contact_form.addEventListener('submit', function(event) {