Polished up callable support so it works properly.

mentoring/light_children.py

@@ -126,7 +126,9 @@ class LightChildrenMixin(XBlockWithChildrenFragmentsMixin):
         Load light children from the `xml_content` attribute
         """
         self.light_children = []
-        if not hasattr(self, 'xml_content') or not self.xml_content:
+        no_content = (not hasattr(self, 'xml_content') or not self.xml_content
+                      or callable(self.xml_content))
+        if no_content:
             return
 
         parser = etree.XMLParser(remove_comments=True)

mentoring/mentoring.py

@@ -49,7 +49,8 @@ log = logging.getLogger(__name__)
 
 def default_xml_content():
     return render_template('templates/xml/mentoring_default.xml', {
-        'url_name': 'mentoring-{}'.format(uuid.uuid4())})
+            'url_name': 'mentoring-{}'.format(uuid.uuid4())})
+
 
 # Classes ###########################################################
 
@@ -99,6 +100,8 @@ class MentoringBlock(XBlockWithLightChildren, StepParentMixin):
 
     FLOATING_BLOCKS = (TitleBlock, MentoringMessageBlock, SharedHeaderBlock)
 
+    FIELDS_TO_INIT = ('xml_content',)
+
     @property
     def is_assessment(self):
         return self.mode == 'assessment'