Show policy, grading policy, and top-level errors

* Save errors for courses that failed to load in modulestore
* global staff can see course errors on their dashboard
* put policy loading errors into the error trackers
* add has_access(user, 'global', 'staff'), which is equiv to user.is_staff for now

lms/djangoapps/courseware/access.py

@@ -63,6 +63,9 @@ def has_access(user, obj, action):
     if isinstance(obj, Location):
         return _has_access_location(user, obj, action)
 
+    if isinstance(obj, basestring):
+        return _has_access_string(user, obj, action)
+
     # Passing an unknown object here is a coding error, so rather than
     # returning a default, complain.
     raise TypeError("Unknown object type in has_access(): '{0}'"
@@ -238,6 +241,30 @@ def _has_access_location(user, location, action):
     return _dispatch(checkers, action, user, location)
 
 
+def _has_access_string(user, perm, action):
+    """
+    Check if user has certain special access, specified as string.  Valid strings:
+
+    'global'
+
+    Valid actions:
+
+    'staff' -- global staff access.
+    """
+
+    def check_staff():
+        if perm != 'global':
+            debug("Deny: invalid permission '%s'", perm)
+            return False
+        return _has_global_staff_access(user)
+
+    checkers = {
+        'staff': check_staff
+        }
+
+    return _dispatch(checkers, action, user, perm)
+
+
 #####  Internal helper methods below
 
 def _dispatch(table, action, user, obj):
@@ -266,6 +293,15 @@ def _course_staff_group_name(location):
     """
     return 'staff_%s' % Location(location).course
 
+def _has_global_staff_access(user):
+    if user.is_staff:
+        debug("Allow: user.is_staff")
+        return True
+    else:
+        debug("Deny: not user.is_staff")
+        return False
+
+
 def _has_staff_access_to_location(user, location):
     '''
     Returns True if the given user has staff access to a location.  For now this

lms/djangoapps/courseware/courses.py

@@ -30,7 +30,6 @@ def get_course_by_id(course_id):
         raise Http404("Course not found.")
 
 
-
 def get_course_with_access(user, course_id, action):
     """
     Given a course_id, look up the corresponding course descriptor,