Catch validation errors raised during studio editing

xblockutils/public/studio_edit.js

@@ -81,6 +81,10 @@ function StudioEditableXBlockMixin(runtime, element) {
             if (jqXHR.responseText) { // Is there a more specific error message we can show?
                 try {
                     message = JSON.parse(jqXHR.responseText).error;
+                    if (typeof message === "object" && message.messages) {
+                        // e.g. {"error": {"messages": [{"text": "Unknown user 'bob'!", "type": "error"}, ...]}} etc.
+                        message = $.map(message.messages, function(msg) { return msg.text; }).join(", ");
+                    }
                 } catch (error) { message = jqXHR.responseText.substr(0, 300); }
             }
             runtime.notify('error', {title: gettext("Unable to update settings"), message: message});

xblockutils/studio_editable.py

@@ -26,6 +26,8 @@ from xblockutils.resources import ResourceLoader
 log = logging.getLogger(__name__)
 loader = ResourceLoader(__name__)
 
+# Classes ###########################################################
+
 
 class FutureFields(object):
     """
@@ -35,6 +37,7 @@ class FutureFields(object):
         self._new_fields_dict = new_fields_dict
         self._blacklist = newly_removed_fields
         self._fallback_obj = fallback_obj
+
     def __getattr__(self, name):
         try:
             return self._new_fields_dict[name]