Make conditional module and poll modules a little easier to understand

common/lib/xmodule/xmodule/conditional_module.py

@@ -96,7 +96,11 @@ class ConditionalModule(ConditionalFields, XModule):
             xml_value = self.descriptor.xml_attributes.get(xml_attr)
             if xml_value:
                 return xml_value, attr_name
-        raise Exception('Error in conditional module: unknown condition "%s"' % xml_attr)
+        raise Exception(
+            'Error in conditional module: no known conditional found in {!r}'.format(
+                self.descriptor.xml_attributes.keys()
+            )
+        )
 
     @lazy
     def required_modules(self):

common/lib/xmodule/xmodule/poll_module.py

@@ -32,7 +32,9 @@ class PollFields(object):
     poll_answer = String(help="Student answer", scope=Scope.user_state, default='')
     poll_answers = Dict(help="All possible answers for the poll fro other students", scope=Scope.user_state_summary)
 
+    # List of answers, in the form {'id': 'some id', 'text': 'the answer text'}
     answers = List(help="Poll answers from xml", scope=Scope.content, default=[])
+
     question = String(help="Poll question", scope=Scope.content, default='')