Making this change I end up with:

```scala
private[python] class ConverterRegistry extends Logging {

  var keyConverter: Converter[Any, Any] = DefaultConverter
  var valueConverter: Converter[Any, Any] = DefaultConverter

...

  private def register(converterClass: String): Converter[Any, Any] = {
    Try {
      val converter = Class.forName(converterClass).newInstance().asInstanceOf[Converter[Any, Any]]
      converter
    } match {
      case Success(s) => s
      case Failure(err) =>
        logError(s"Failed to register converter: $converterClass")
        throw err
    }
  }
```

Is this the best approach or is there another better way?