Maintenance: detect missing parent::__construct()

The first time I forgot to include that line in a maintenance script,
I spent a few minutes debugging "Notice: Undefined variable: IP".
Hopefully, this change will save someone else a few minutes of his
or her own time.

Change-Id: Icd26a5dc59e25d2bcc6da9bf0a2f6e95d494e5a6
Merge "Maintenance: detect missing parent::__construct()"