Missing error indicator for checkboxes (Valo theme)

• Vaadin version: 8.0.4

There is no error indicator for checkboxes except the exclamation mark. there should be a background color change and even a border color change like textfeld. i did it as a workaround like this:

`@mixin valo-checkbox ($primary-stylename: v-checkbox, $include-additional-styles: contains($v-included-additional-styles, checkbox)) {

.#{$primary-stylename} {
    @include valo-checkbox-style;
}

.#{$primary-stylename}-error {
    > input ~ label:before {
        border-style: dashed !important;
        border-color: $v-error-indicator-color !important;
        $bg: scale-color($v-error-indicator-color, $lightness: 98%);
        background: $bg !important;
        color: valo-font-color($bg);
    }
}


@if $include-additional-styles {
    .#{$primary-stylename}-small {
        @include valo-checkbox-style($unit-size: $v-unit-size--small);
        font-size: $v-font-size--small;
    }

    .#{$primary-stylename}-large {
        @include valo-checkbox-style($unit-size: $v-unit-size--large);
        font-size: $v-font-size--large;
    }
}

}
`
so if you set the checkbox as required and validate it, there should be a red border and a very light red background.

Start with the Valo theme's checkbox styling and compare it with the text field error styling described in the issue and workaround. Verify that a required checkbox in a validation error state shows a red border and a very light red background, in addition to the existing indicator.