Prettier error display

* Log formatted traceback string instead of exc_info tuple itself
* display as a list

common/lib/xmodule/xmodule/errortracker.py

 import logging
 import sys
+import traceback
 
 from collections import namedtuple
 
@@ -14,21 +15,21 @@ def in_exception_handler():
 
 def make_error_tracker():
     '''Return an ErrorLog (named tuple), with fields (tracker, errors), where
-    the logger appends a tuple (message, exc_info=None)
-    to the errors on every call.
+    the logger appends a tuple (message, exception_str) to the errors on every
+    call.  exception_str is in the format returned by traceback.format_exception.
 
-    error_list is a simple list.  If the caller messes with it, info
+    error_list is a simple list.  If the caller modifies it, info
     will be lost.
     '''
     errors = []
 
     def error_tracker(msg):
         '''Log errors'''
-        exc_info = None
+        exc_str = ''
         if in_exception_handler():
-            exc_info = sys.exc_info()
+            exc_str = ''.join(traceback.format_exception(*sys.exc_info()))
 
-        errors.append((msg, exc_info))
+        errors.append((msg, exc_str))
 
     return ErrorLog(error_tracker, errors)
 

lms/templates/courseware.html

@@ -51,7 +51,13 @@
       % if course_errors is not UNDEFINED:
           <h2>Course errors</h2>
           <div id="course-errors">
-            ${course_errors}
+            <ul>
+          % for (msg, err) in course_errors:
+            <li>${msg}
+              <ul><li><pre>${err}</pre></li></ul>
+            </li>
+          % endfor
+            </ul>
           </div>
       % endif
     </section>