script: Catch any exceptions when trying to access network

If anything goes wrong with network access, instead of crashing the
script, the script should instead switch to red LED and try again
after a brief delay.

Signed-off-by: Greg Meiste <greg.meiste@gmail.com>
backend: Add power outage notifier task. Needed for issue #5

Google App Engine does not allow reuse of task names, and purge() is
asynchronous, so the generated task name must be saved for later use.

Signed-off-by: Greg Meiste <greg.meiste@gmail.com>