Upgrade djangorestframework to v3.1

* Upgrade edx-submissions
* Upgrade edx-ora2
* Upgrade edx-val
* Upgrade edx-proctoring
* Update all edx-platform code that depends on DRF, including:
  - auth_exchange
  - cors_csrf
  - embargo
  - enrollment
  - util
  - commerce
  - course_structure
  - discussion_api
  - mobile_api
  - notifier_api
  - teams
  - credit
  - profile_images
  - user_api
  - lib/api (OAuth2 and pagination)

lms/djangoapps/course_structure_api/v0/serializers.py

@@ -11,11 +11,11 @@ class CourseSerializer(serializers.Serializer):
     id = serializers.CharField()  # pylint: disable=invalid-name
     name = serializers.CharField(source='display_name')
     category = serializers.CharField()
-    org = serializers.SerializerMethodField('get_org')
-    run = serializers.SerializerMethodField('get_run')
-    course = serializers.SerializerMethodField('get_course')
-    uri = serializers.SerializerMethodField('get_uri')
-    image_url = serializers.SerializerMethodField('get_image_url')
+    org = serializers.SerializerMethodField()
+    run = serializers.SerializerMethodField()
+    course = serializers.SerializerMethodField()
+    uri = serializers.SerializerMethodField()
+    image_url = serializers.SerializerMethodField()
     start = serializers.DateTimeField()
     end = serializers.DateTimeField()
 

lms/djangoapps/course_structure_api/v0/views.py

@@ -6,7 +6,8 @@ import logging
 
 from django.conf import settings
 from django.http import Http404
-from rest_framework.authentication import OAuth2Authentication, SessionAuthentication
+from rest_framework.authentication import SessionAuthentication
+from rest_framework_oauth.authentication import OAuth2Authentication
 from rest_framework.exceptions import AuthenticationFailed, ParseError
 from rest_framework.generics import RetrieveAPIView, ListAPIView
 from rest_framework.permissions import IsAuthenticated
@@ -21,7 +22,6 @@ from courseware.access import has_access
 from courseware.model_data import FieldDataCache
 from courseware.module_render import get_module_for_descriptor
 from openedx.core.lib.api.view_utils import view_course_access, view_auth_classes
-from openedx.core.lib.api.serializers import PaginationSerializer
 from openedx.core.djangoapps.content.course_structures.api.v0 import api, errors
 from student.roles import CourseInstructorRole, CourseStaffRole
 from util.module_utils import get_dynamic_descriptor_children
@@ -157,9 +157,6 @@ class CourseList(CourseViewMixin, ListAPIView):
             * end: The course end date. If course end date is not specified, the
               value is null.
     """
-    paginate_by = 10
-    paginate_by_param = 'page_size'
-    pagination_serializer_class = PaginationSerializer
     serializer_class = serializers.CourseSerializer
 
     def get_queryset(self):