Fix the broken validations test

The validation error box function was not searching the right place
for the appropriate component.
Instead of repeating `transUnitCol`, `1` and `gwt-DisclosurePanel`, perhaps we could extract constants to reuse?

Or better still, extract a method like:

    Element findGwtDisclosurePanel(Driver driver) {
        return driver.findElement(By.className("selected"))
            .findElements(By.className("transUnitCol"))
            .get(1) // Right column
            .findElement(By.className("gwt-DisclosurePanel"))
    }

And use it in all four places.