Allow StandardErrorLoggingHandler to be used

config-templates/config.php

@@ -264,7 +264,7 @@ $config = [
      *
      * Choose logging handler.
      *
-     * Options: [syslog,file,errorlog]
+     * Options: [syslog,file,errorlog,stderr]
      *
      */
     'logging.level' => SimpleSAML\Logger::NOTICE,
@@ -800,7 +800,7 @@ $config = [
      * \SimpleSAML\XHTML\TemplateControllerInterface interface to use it.
      */
     //'theme.controller' => '',
-    
+
     /*
      * Templating options
      *

lib/SimpleSAML/Logger.php

@@ -356,6 +356,7 @@ class Logger
             'syslog'   => 'SimpleSAML\Logger\SyslogLoggingHandler',
             'file'     => 'SimpleSAML\Logger\FileLoggingHandler',
             'errorlog' => 'SimpleSAML\Logger\ErrorLogLoggingHandler',
+            'stderr' => 'SimpleSAML\Logger\StandardErrorLoggingHandler',
         ];
 
         // get the configuration