Cause: The new key content had an extra newline at the end. Consequence: The test to see if the new key content was in the current authorized_key list failed, so the key was added every time, and the task was not idempotent. Fix: Ensure the new key value has no extra newline. Use a simple list `in` test to see if the new value is in the existing list. Result: The task to write authorized_keys is idempotent.