When using mod_auth_kerb and "Extension:Auth_remoteuser" you need to do the following:
In apache's vhost config, make sure that calls from 127.0.0.1 are not blocked by mod_auth_kerb:
<VirtualHost *:443>
...
<Directory /var/www/bluespice>
...
<RequireAny>
AuthType Kerberos
...
Require ip 127.0.0.0/255.0.0.0 #PhantomJS
</RequireAny>
</Directory>
...
Also set in LocalSettings.php:
$bsgArticlePreviewCapturePhantomJSBaseUrl = 'http://localhost';
For "Extension:Auth_remoteuser" configure
$wgAuthRemoteuserUserName = [
isset( $_SERVER[ 'REMOTE_USER' ] ) ? $_SERVER[ 'REMOTE_USER' ] : '',
$_SERVER[ 'REMOTE_ADDR' ] == '127.0.0.1' ? $_COOKIE['<cookieprefix>RemoteToken'] : '', //e.g. PhantomJS
...
];
Be aware that <cookieprefix> must be set to a valid value!
If you want to use symfony-process as a backend for PhantomJS, make sure that you have installed needed package.
You can do it easily by adding symfony/process package into your composer.lock and run composer install