default void visitSpecAnnotation(T annotation, SpecInfo spec) {
    throw new InvalidSpecException("@%s may not be applied to Specs")
      .withArgs(annotation.annotationType().getSimpleName());
  }
Handles the annotation when applied to a specification.
The default implementation of this method throws an {@link InvalidSpecException}.
This method is not called by Spock directly, but only by the default implementation of
{@link #visitSpecAnnotations(List, SpecInfo)}, so if you have overwritten that method,
there is no need to overwrite this one too except if you want to call it yourself.

@param annotation the annotation found on the specification
@param spec       the annotated specification
spock-core/src/main/java/org/spockframework/runtime/extension/IAnnotationDrivenExtension.java