ExclusiveLockFailedError for Files API in Google App Engine
Make sure you use the statement:
from __future__ import with_statement
at the very top of you file.
Use the "with" syntax as done on the Google App Engine documentation at http://code.google.com/appengine/docs/python/blobstore/overview.html.
Failure to do so will result in an ExclusiveLockFailedError.
-Raj
