diff --git a/lms/djangoapps/discussion/notification_prefs/tests.py b/lms/djangoapps/discussion/notification_prefs/tests.py
index 6a665160e3..6efe5e3f90 100644
--- a/lms/djangoapps/discussion/notification_prefs/tests.py
+++ b/lms/djangoapps/discussion/notification_prefs/tests.py
@@ -53,7 +53,7 @@ class NotificationPrefViewTest(UrlResetMixin, TestCase):
     def create_prefs(self):
         """Create all test preferences in the database"""
         for (user, token) in self.tokens.items():
-            UserPreference.objects.create(user=user, key=NOTIFICATION_PREF_KEY, value=token)
+            UserPreference.objects.get_or_create(user=user, key=NOTIFICATION_PREF_KEY, value=token)
 
     def assertPrefValid(self, user):
         """Ensure that the correct preference for the user is persisted"""
diff --git a/lms/djangoapps/discussion/notification_prefs/views.py b/lms/djangoapps/discussion/notification_prefs/views.py
index d9411c50b8..a91996e623 100644
--- a/lms/djangoapps/discussion/notification_prefs/views.py
+++ b/lms/djangoapps/discussion/notification_prefs/views.py
@@ -71,7 +71,7 @@ class UsernameCipher(object):
         encryptor = aes_cipher.encryptor()
         padder = PKCS7(AES.block_size).padder()
         padded = padder.update(username.encode("utf-8")) + padder.finalize()
-        return urlsafe_b64encode(initialization_vector + encryptor.update(padded) + encryptor.finalize())
+        return urlsafe_b64encode(initialization_vector + encryptor.update(padded) + encryptor.finalize()).decode()
 
     @staticmethod
     def decrypt(token):
@@ -187,7 +187,7 @@ def set_subscription(request, token, subscribe):  # pylint: disable=unused-argum
     success, the response will contain a page indicating success.
     """
     try:
-        username = UsernameCipher().decrypt(token.encode())
+        username = UsernameCipher().decrypt(token.encode()).decode()
         user = User.objects.get(username=username)
     except UnicodeDecodeError:
         raise Http404("base64url")
diff --git a/lms/djangoapps/discussion/rest_api/forms.py b/lms/djangoapps/discussion/rest_api/forms.py
index 05b1f367dc..85a879a7b9 100644
--- a/lms/djangoapps/discussion/rest_api/forms.py
+++ b/lms/djangoapps/discussion/rest_api/forms.py
@@ -167,7 +167,7 @@ class CourseDiscussionRolesForm(CourseDiscussionSettingsForm):
         (FORUM_ROLE_GROUP_MODERATOR, FORUM_ROLE_GROUP_MODERATOR),
     )
     rolename = ChoiceField(
-        ROLE_CHOICES,
+        choices=ROLE_CHOICES,
         error_messages={u"invalid_choice": u"Role '%(value)s' does not exist"}
     )