I use $CFG->langlocalroot and $CFG->langotherroot to point my Moodle install at an alternative location for language packs than $CFG->dataroot/lang so the lang folder does not exist at $CFG->dataroot.

When I try to load the 'package a flavour' link in my browser, it eventually gives a time-out.

By digging in the code a bit, I can see that the loop is being entered in get_system_customlangs() even though the opendir() on $this->langpath returned false.