[horde] Passwd 5.0.0RC1: Composite driver and Expect params

[Oscar del Rio]

I just installed Passwd H5 (5.0.0RC1).

The Expect driver works well by itself, with the following backend.local.php

  $backends['expect']['disabled'] = false;
  $backends['expect']['params']['script'] = PASSWD_BASE . 
'/scripts/passwd-expect';
  $backends['expect']['params']['params'] = '-host servername';

The successful command called by Driver/Expect.php is

LANG=C LC_ALL=C /usr/bin/expect -f 
'/horde/passwd/lib/../scripts/passwd-expect' -- -host servername -log 
'/var/tmp/passwdZ4aqha'

I am now trying to use Expect with the Composite driver:

$backends['combo'] = array(
     'disabled' => false,
     'name' => 'Passwords',
     'driver' => 'Composite',
     'policy' => array(
         'minLength' => 6,
         'minNumeric' => 1,
     ),
     'params' => array('drivers' => array(
         'expect' => array(
             'name' => 'Unix Server',
             'driver' => 'Expect',
             'required' => true,
             'params' => array(
                 'program' => '/usr/bin/expect',
                 'script' => PASSWD_BASE . '/scripts/passwd-expect',
                 'params' => '-host servername',
             ),
         ),
         'samba' => array(
             'name' => 'Samba Server',
             'driver' => 'Smbpasswd',
             'params' => array(
                 'program' => '/usr/bin/smbpasswd',
                 'host' => 'sambaserver',
             ),
         ),
     )),
);

But Expect is failing.  Debugging the code in Driver/Expect.php, the 
command that it is trying to execute is

LANG=C LC_ALL=C /usr/bin/expect -f 
'/horde/passwd/lib/../scripts/passwd-expect' -- Array -log 
'/var/tmp/passwdiBa4pa'

Note "Array" in the command instead of the script params "-host 
servername"  ($this->_params['params'] in the Expect.php code)

Am I doing something wrong in the composite backend definition or is 
this a bug?

Thanks!