asana-task-complete doesn't complete the task as expected. Instead, it fails for an unknown (to me, yet) reason.
Note that completing with CURL does work:
curl -X PUT https://app.asana.com/api/1.0/tasks/<task_id> \
-H "Authorization: Bearer <auth>" \
-H "Content-Type: application/json" \
-d '{"data":{"completed":true}}'