code: @Nonnull
    public ValidationResultList executeValidation (@Nonnull final IValidationSource aSource,
                                                   @Nullable final Locale aLocale)
    {
      final ValidationResultList ret = new ValidationResultList ();
      executeValidation (aSource, ret, aLocale);
      return ret;
    }
docs: Perform a validation with all the contained executors.
  
  @param aSource
  The source artefact to be validated. May not be <code>null</code>.
  @param aLocale
  Custom locale to use e.g. for error messages. May be
  <code>null</code> to use the system default locale.
  @return The validation result list. Never <code>null</code>. For each
  contained executor a result is added to the result list.
  @see #executeValidation(IValidationSource, ValidationResultList, Locale)