fix(msgPool) Improve siError formatting

issue #6172

include/class_msgPool.inc

@@ -569,7 +569,7 @@ class msgPool
     if ($error == '') {
       return htmlescape(_('Communication failure with the infrastructure service!'));
     }
-    return sprintf(htmlescape(_('Communication failure with the infrastructure service: %s')), '<br/><br/>'.htmlescape(sprintf(_('Error: %s'), $error)));
+    return nl2br(htmlescape(sprintf(_("Communication failure with the infrastructure service: %s\n\nError: %s"), $error)));
   }
 
   /*!

include/class_msg_dialog.inc

@@ -116,7 +116,7 @@ class msg_dialog
    *
    * \param string|object $title The title of the message dialog, or the error object
    *
-   * \param string $message The message of the message dialog
+   * \param string $message The message of the message dialog (HTML)
    *
    * \param int $type The type of the message dialog, by default = INFO_DIALOG
    *