change error HTTP response codes to 400 where appropriate

lms/djangoapps/shoppingcart/tests/test_views.py

@@ -63,14 +63,14 @@ class ShoppingCartViewsTests(ModuleStoreTestCase):
         PaidCourseRegistration.add_to_order(self.cart, self.course_id)
         self.login_user()
         resp = self.client.post(reverse('shoppingcart.views.add_course_to_cart', args=[self.course_id]))
-        self.assertEqual(resp.status_code, 404)
+        self.assertEqual(resp.status_code, 400)
         self.assertIn(_('The course {0} is already in your cart.'.format(self.course_id)), resp.content)
 
     def test_add_course_to_cart_already_registered(self):
         CourseEnrollment.enroll(self.user, self.course_id)
         self.login_user()
         resp = self.client.post(reverse('shoppingcart.views.add_course_to_cart', args=[self.course_id]))
-        self.assertEqual(resp.status_code, 404)
+        self.assertEqual(resp.status_code, 400)
         self.assertIn(_('You are already registered in course {0}.'.format(self.course_id)), resp.content)
 
     def test_add_nonexistent_course_to_cart(self):

lms/djangoapps/shoppingcart/views.py

 import logging
-from django.http import HttpResponse, HttpResponseRedirect, HttpResponseNotFound, HttpResponseForbidden, Http404
+from django.http import (HttpResponse, HttpResponseRedirect, HttpResponseNotFound,
+    HttpResponseBadRequest, HttpResponseForbidden, Http404)
 from django.utils.translation import ugettext as _
 from django.views.decorators.http import require_POST
 from django.core.urlresolvers import reverse
@@ -19,9 +20,9 @@ def add_course_to_cart(request, course_id):
         return HttpResponseForbidden(_('You must be logged-in to add to a shopping cart'))
     cart = Order.get_cart_for_user(request.user)
     if PaidCourseRegistration.part_of_order(cart, course_id):
-        return HttpResponseNotFound(_('The course {0} is already in your cart.'.format(course_id)))
+        return HttpResponseBadRequest(_('The course {0} is already in your cart.'.format(course_id)))
     if CourseEnrollment.is_enrolled(user=request.user, course_id=course_id):
-        return HttpResponseNotFound(_('You are already registered in course {0}.'.format(course_id)))
+        return HttpResponseBadRequest(_('You are already registered in course {0}.'.format(course_id)))
     try:
         PaidCourseRegistration.add_to_order(cart, course_id)
     except ItemNotFoundError: