public String getRequiredString(List<String> keyAliases, Predicate<String> constraint, String message) {
        return Optional
            .ofNullable(getString(keyAliases, null, constraint, message))
            .orElseThrow(() -> InvalidOptionConfigurationException.requiredValue(keyAliases, "string"));
    }
As {@link #getString(List, String, Predicate, String)}, but additionally throw an exception if no value
is provided.

@throws InvalidOptionConfigurationException if a constraint violation occurs or if no value was provided.
@see #getString(List, String, Predicate, String)
common/config/src/main/java/io/apiman/common/config/options/GenericOptionsParser.java