I would handle it something different. Or you configure the route_basepaths option or the route_basepath, but not both. It'll look like:

```php
->validate()
    ->ifTrue(function ($v) { isset($v['route_basepath']) && isset($v['route_basepaths']); })
    ->thenInvalid('You can't configure both "route_basepath" and "route_basepaths", use "route_basepaths".')
->end()
```