I installed mod_auth_external for 0.8.2 on ubuntu 12.04 but it's not working. I have external_auth_command = "/home/yang/chat/testing" but it's not getting invoked. I enabled debug logging and see no messages from that mod. Any help?

I'm using the Candy example client. Here's what's written to the log after I submit a login request (and nothing in err log):

Oct 24 21:02:43 socket        debug   server.lua: accepted new client connection from 127.0.0.1:40527 to 5280
Oct 24 21:02:43 mod_bosh        debug   BOSH body open (sid: %s)
Oct 24 21:02:43 boshb344ba85-fbf5-4a26-b5f5-5bd35d5ed372        debug   BOSH session created for request from 169.254.11.255
Oct 24 21:02:43 mod_bosh        info    New BOSH session, assigned it sid 'b344ba85-fbf5-4a26-b5f5-5bd35d5ed372'
Oct 24 21:02:43 httpserver      debug   Sending response to bf9120
Oct 24 21:02:43 httpserver      debug   Destroying request bf9120
Oct 24 21:02:43 httpserver      debug   Request has destroy callback
Oct 24 21:02:43 socket  debug   server.lua: closed client handler and removed socket from list
Oct 24 21:02:43 mod_bosh        debug   Session b344ba85-fbf5-4a26-b5f5-5bd35d5ed372 has 0 out of 1 requests open
Oct 24 21:02:43 mod_bosh        debug   and there are 0 things in the send_buffer
Oct 24 21:02:43 socket  debug   server.lua: accepted new client connection from 127.0.0.1:40528 to 5280
Oct 24 21:02:43 mod_bosh        debug   BOSH body open (sid: b344ba85-fbf5-4a26-b5f5-5bd35d5ed372)
Oct 24 21:02:43 mod_bosh        debug   Session b344ba85-fbf5-4a26-b5f5-5bd35d5ed372 has 1 out of 1 requests open
Oct 24 21:02:43 mod_bosh        debug   and there are 0 things in the send_buffer
Oct 24 21:02:43 mod_bosh        debug   Have nothing to say, so leaving request unanswered for now
Oct 24 21:02:43 httpserver      debug   Request c295d0 left open, on_destroy is function(mod_bosh.lua:81)

Here's the config I added:

modules_enabled = {
    ...
    "bosh"; -- Enable BOSH clients, aka "Jabber over HTTP"
    ...
}

authentication = "external"
external_auth_protocol = "generic"
external_auth_command = "/home/yang/chat/testing"