ErrorHandler not being called with HystrixJS Commands wrapped around SailsJS controller calls to DB

I'm having some difficulting getting HystrixJS to work with my SailsJS controller calls to the database. I want to wrap each request to the database in a hystrix command. I seem to be able to wrap the calls in a command and have a successfully response. But when I force return an error, the isErrorHandler is not called, placing some logs in the Command.js lib folder shows it is still calling the successHandler. How would I go about making sure the isErrorHandler is being called properly when an error is returned from my wrapped function? Below is some example code I'm working with for getting a list of users. Thank you for any help.

getUsers: function(req, res, next) {
    // call to wrapped by hystrix command
    function promiseCall() {
        var deferred = Q.defer();

        User.find().exec(function (err, users) {
            // i know users will be returned, trying fo force the isErrorHandlers
            if(users) {
                deferred.reject(new Error("No Users"));
                return res.serverError();
            }

            deferred.resolve();
            res.json(users);
        })

        return deferred.promise; 
    }

    var isErrorHandler = function(error) {
        console.log('error caught', error);
        if (error) {
            return error;
        }
        if (error.statusCode == 503) {
            var unavailableError = new Error();
            unavailableError.name = "ServiceUnavailableError";
            return unavailableError;
        }
        return null;
    };

    var fallback = function (error) {
        console.log('fallback', error);
    }

    var serviceCommand = CommandsFactory.getOrCreate("get users")     
        .circuitBreakerErrorThresholdPercentage(50)     
        .timeout(10000)     
        .run(promiseCall)
        .circuitBreakerRequestVolumeThreshold(10)     
        .circuitBreakerSleepWindowInMilliseconds(3000)            
        .errorHandler(isErrorHandler)
        .fallbackTo(fallback)     
        .build();
    console.log('call promise');

    var promise = serviceCommand.execute();
}

via Trevor