namespaceDupes.php thinks all wikis have a interwiki table. But that is not always
the case for older wikis even though they have run update.php faithfully even thru 1.15:
$ php namespaceDupes.php
Warning: Invalid argument supplied for foreach() in /home/jidanni/phase3/maintenance/namespaceDupes.php on line 59
Version: 1.15.x
Severity: trivial