This event occurs when a package changes status (for example, when a package is cancelled it goes from an "active" status to a "cancelled" status).

Note these fields:

context_str = package
context_id = ... (this will be the package_id value of the package that changed)
event = status

Your script should examine these attributes to determine the new status of the package:

Your script may also wish to observe the package.package_status_name attribute, which provides a human-friendly status value.