Some exceptions do not contain a message

E.g. InvocationTargetException thrown when a class cannot be instantiated
does not contain a message, resulting in a NPE exception in specs,
making the stacktrace useless.

java.lang.Exception: Could not instantiate class XSpec: null

for the test

import org.specs2.mutable.Specification

class XSpec extends Specification {

  val tested = new TestedComponent

  "A spec" should {
    "not fail with NPE" in {
      success
    }
  }

}

case class MyException(message: String) extends
RuntimeException(message)

class TestedComponent {

  val value = {
    // This causes a InvocationTargetException with a null message,
    // resulting in the stack trace from specs:
    // java.lang.Exception: Could not instantiate class XSpec: null
    if (1 == 1) throw new MyException("Oops")
    "Oops"
  }
}