make ENABLE_SHOPPING_CART truly optional

course_about was throwing 500s if ENABLE_SHOPPING_CART=False

lms/djangoapps/courseware/views.py

@@ -609,7 +609,8 @@ def course_about(request, course_id):
     registration_price = 0
     in_cart = False
     reg_then_add_to_cart_link = ""
-    if settings.MITX_FEATURES.get('ENABLE_PAID_COURSE_REGISTRATION'):
+    if (settings.MITX_FEATURES.get('ENABLE_SHOPPING_CART') and
+        settings.MITX_FEATURES.get('ENABLE_PAID_COURSE_REGISTRATION')):
         registration_price = CourseMode.min_course_price_for_currency(course_id,
                                                                       settings.PAID_COURSE_REGISTRATION_CURRENCY[0])
         if request.user.is_authenticated():

lms/templates/courseware/course_about.html

@@ -3,8 +3,12 @@
   from django.core.urlresolvers import reverse
   from courseware.courses import course_image_url, get_course_about_section
   from courseware.access import has_access
+  from django.conf import settings
 
+  if settings.MITX_FEATURES.get('ENABLE_SHOPPING_CART'):
       cart_link = reverse('shoppingcart.views.show_cart')
+  else:
+      cart_link = ""
 %>
 <%namespace name='static' file='../static_content.html'/>
 
@@ -26,6 +30,8 @@
       $("#class_enroll_form").submit();
       event.preventDefault();
     });
+
+    % if settings.MITX_FEATURES.get('ENABLE_SHOPPING_CART') and settings.MITX_FEATURES.get('ENABLE_PAID_COURSE_REGISTRATION'):
       add_course_complete_handler = function(jqXHR, textStatus) {
         if (jqXHR.status == 200) {
           location.href = "${cart_link}";
@@ -48,7 +54,7 @@
         })
         event.preventDefault();
       });
-
+    % endif
 
     ## making the conditional around this entire JS block for sanity
     %if settings.MITX_FEATURES.get('RESTRICT_ENROLL_BY_REG_METHOD') and course.enrollment_domain:

lms/templates/navigation.html

@@ -84,7 +84,7 @@ site_status_msg = get_site_status_msg(course_id)
       </li>
     </ol>
       % if settings.MITX_FEATURES.get('ENABLE_PAID_COURSE_REGISTRATION') and \
-           settings.MITX_FEATURES['ENABLE_SHOPPING_CART'] and \
+           settings.MITX_FEATURES.get('ENABLE_SHOPPING_CART') and \
            shoppingcart.models.Order.user_cart_has_items(user):
         <ol class="user">
           <li class="primary">