Log errors in external grader message parsing

common/lib/capa/capa/responsetypes.py

@@ -1210,13 +1210,13 @@ class CodeResponse(LoncapaResponse):
         try:
             score_result = json.loads(score_msg)
         except (TypeError, ValueError):
-            log.error("External grader message should be a JSON-serialized dict")
+            log.error("External grader message should be a JSON-serialized dict. Received score_msg = %s" % score_msg)
             return fail
         if not isinstance(score_result, dict):
-            log.error("External grader message should be a JSON-serialized dict")
+            log.error("External grader message should be a JSON-serialized dict. Received score_result = %s" % score_result)
             return fail
         for tag in ['correct', 'score', 'msg']:
-            if not score_result.has_key(tag):
+            if tag not in score_result:
                 log.error("External grader message is missing one or more required tags: 'correct', 'score', 'msg'")
                 return fail