Consolidate access checks for prereqs and surveys.

lms/djangoapps/courseware/exceptions.py

@@ -15,5 +15,13 @@ class Redirect(Exception):
 class CourseAccessRedirect(Redirect):
     """
     Redirect raised when user does not have access to a course.
+
+    Arguments:
+        url (string): The redirect url.
+        access_error (AccessErro): The AccessError that caused the redirect.
+            The AccessError contains messages for developers and users explaining why
+            the user was denied access. These strings can then be exposed to the user.
     """
-    pass
+    def __init__(self, url, access_error=None):
+        super(CourseAccessRedirect, self).__init__(url)
+        self.access_error = access_error