Gracefully handle any errors that occur when attempting to remove the rollback handler.
Gracefully handle any errors that occur when attempting to remove the rollback
handler.

Fixes Issue #64.



git-svn-id: 7c59d995a3d63779dc3f8cdf6830411bfeeaa67b@48 d4307497-c249-0410-99bd-594fbd7e173e

clones/google-app-engine-django,wtanaka/google-app-engine-helper-for-django