Call to member function of non-object: setDebug()

On line 543 of /libraries/joomla/installer/adapters/template.php there is a call
to the $lang object, but that object doesn't exist. Within the
discover_install() function, there is no call to $lang =
JFactory::getLanguage(). This causes the template install via Discover to fail.
The template partially intalls, but no Style is created, so you can't actually
use the template.

To fix it, just add $lang = JFactory::getLanguage(); to the discover_install()
function on line 503.