function showValidationMessage(error) {
  const domCache = privateProps.domCache.get(this)
  const params = privateProps.innerParams.get(this)
  dom.setInnerHtml(domCache.validationMessage, error)
  domCache.validationMessage.className = swalClasses['validation-message']
  if (params.customClass && params.customClass.validationMessage) {
    dom.addClass(domCache.validationMessage, params.customClass.validationMessage)
  }
  dom.show(domCache.validationMessage)

  const input = this.getInput()
  if (input) {
    input.setAttribute('aria-invalid', 'true')
    input.setAttribute('aria-describedby', swalClasses['validation-message'])
    dom.focusInput(input)
    dom.addClass(input, swalClasses.inputerror)
  }
}
Show block with validation message

@param {string} error
@this {SweetAlert}