Description:
------------
gettext works fine on one server, the precisely same source and .mo-Files fail to work on another (same OS, same PHP versions).

Reproduce code:
---------------
See some minimal gettext sample code on the web like the one below, it happens with all, really. 
<?php
setlocale(LC_MESSAGES,'az_AZ');
bindtextdomain("test","./locale");
textdomain("test");

echo _("text to translate");
?>

Expected result:
----------------
I would have expected gettext to work the same on both servers.

Actual result:
--------------
One server returned the expected result, the other just returned the message ID (gettext parameter).

I've found some similar reports on the web and here, but no solution yet; that's why I dug into it. 

Turns out, even if the correct .mo file is in the correct location, gettext fails if the respective *system* locale isn't installed. 
This is (somewhat) documented behaviour. But one doesn't get an exception, log entry or error message - just the default value. Which makes it REALLY hard to debug, especially when the server is a remote web host.

I suggest changing the gettext interface such as not finding the system locales for the selected language (if they are _really_ necessary) throws an Exception the fact. 
That way, people at least know what happened.