Make the django_comment_client return errors that can't be parsed as JSON just…

Make the django_comment_client return errors that can't be parsed as JSON just as simple strings when in an ajax context

lms/djangoapps/django_comment_client/middleware.py

 from comment_client import CommentClientError
 from django_comment_client.utils import JsonError
 import json
+import logging
+
+log = logging.getLogger(__name__)
 
 
 class AjaxExceptionMiddleware(object):
+    """
+    Middleware that captures CommentClientErrors during ajax requests
+    and tranforms them into json responses
+    """
     def process_exception(self, request, exception):
+        """
+        Processes CommentClientErrors in ajax requests. If the request is an ajax request,
+        returns a http response that encodes the error as json
+        """
         if isinstance(exception, CommentClientError) and request.is_ajax():
-            return JsonError(json.loads(exception.message))
+            try:
+                return JsonError(json.loads(exception.message))
+            except ValueError:
+                return JsonError(exception.message)
         return None

lms/djangoapps/django_comment_client/tests/test_middleware.py

-import string
-import random
-import collections
-
 from django.test import TestCase
 
 import comment_client
@@ -13,17 +9,19 @@ class AjaxExceptionTestCase(TestCase):
 
 # TODO: check whether the correct error message is produced.
 # The error message should be the same as the argument to CommentClientError
-        def setUp(self):
-                self.a = middleware.AjaxExceptionMiddleware()
-                self.request1 = django.http.HttpRequest()
-                self.request0 = django.http.HttpRequest()
-                self.exception1 = comment_client.CommentClientError('{}')
-                self.exception0 = ValueError()
-                self.request1.META['HTTP_X_REQUESTED_WITH'] = "XMLHttpRequest"
-                self.request0.META['HTTP_X_REQUESTED_WITH'] = "SHADOWFAX"
+    def setUp(self):
+        self.a = middleware.AjaxExceptionMiddleware()
+        self.request1 = django.http.HttpRequest()
+        self.request0 = django.http.HttpRequest()
+        self.exception1 = comment_client.CommentClientError('{}')
+        self.exception2 = comment_client.CommentClientError('Foo!')
+        self.exception0 = ValueError()
+        self.request1.META['HTTP_X_REQUESTED_WITH'] = "XMLHttpRequest"
+        self.request0.META['HTTP_X_REQUESTED_WITH'] = "SHADOWFAX"
 
-        def test_process_exception(self):
-                self.assertIsInstance(self.a.process_exception(self.request1, self.exception1), middleware.JsonError)
-                self.assertIsNone(self.a.process_exception(self.request1, self.exception0))
-                self.assertIsNone(self.a.process_exception(self.request0, self.exception1))
-                self.assertIsNone(self.a.process_exception(self.request0, self.exception0))
+    def test_process_exception(self):
+        self.assertIsInstance(self.a.process_exception(self.request1, self.exception1), middleware.JsonError)
+        self.assertIsInstance(self.a.process_exception(self.request1, self.exception2), middleware.JsonError)
+        self.assertIsNone(self.a.process_exception(self.request1, self.exception0))
+        self.assertIsNone(self.a.process_exception(self.request0, self.exception1))
+        self.assertIsNone(self.a.process_exception(self.request0, self.exception0))