Change modulestore to use a logging error handler

* log errors, but don't fail

common/lib/xmodule/xmodule/errorhandlers.py

+import logging
 import sys
 
+log = logging.getLogger(__name__)
+
+def in_exception_handler():
+    '''Is there an active exception?'''
+    return sys.exc_info() != (None, None, None)
+
 def strict_error_handler(msg, exc_info=None):
     '''
     Do not let errors pass.  If exc_info is not None, ignore msg, and just
@@ -11,13 +18,26 @@ def strict_error_handler(msg, exc_info=None):
     if exc_info is not None:
         raise exc_info[0], exc_info[1], exc_info[2]
 
-    # Check if there is an exception being handled somewhere up the stack
-    if sys.exc_info() != (None, None, None):
+    if in_exception_handler():
         raise
 
     raise Exception(msg)
 
 
+def logging_error_handler(msg, exc_info=None):
+    '''Log all errors, but otherwise let them pass, relying on the caller to
+    workaround.'''
+    if exc_info is not None:
+        log.exception(msg, exc_info=exc_info)
+        return
+
+    if in_exception_handler():
+        log.exception(msg)
+        return
+
+    log.error(msg)
+
+
 def ignore_errors_handler(msg, exc_info=None):
     '''Ignore all errors, relying on the caller to workaround.
     Meant for use in the LMS, where an error in one part of the course

common/lib/xmodule/xmodule/modulestore/xml.py

@@ -3,7 +3,7 @@ from fs.osfs import OSFS
 from importlib import import_module
 from lxml import etree
 from path import path
-from xmodule.errorhandlers import strict_error_handler
+from xmodule.errorhandlers import logging_error_handler
 from xmodule.x_module import XModuleDescriptor, XMLParsingSystem
 from xmodule.mako_module import MakoDescriptorSystem
 from cStringIO import StringIO
@@ -100,7 +100,7 @@ class XMLModuleStore(ModuleStore):
     """
     def __init__(self, data_dir, default_class=None, eager=False,
                  course_dirs=None,
-                 error_handler=strict_error_handler):
+                 error_handler=logging_error_handler):
         """
         Initialize an XMLModuleStore from data_dir