Accessing full jQuery error information when using Q

jquery_error_q.js

// The Q 'coming from jQuery' wiki page (https://github.com/kriskowal/q/wiki/Coming-from-jQuery) says the following:
//
//     "So if you are used to writing code like
//      $.ajax(...).then(function (data, status, xhr) {
//          console.log(data, status, xhr);
//      });
//      when transitioning to Q [...] you should assume they only return a single object"
//
// That is all well and good, but doesn't address how to access the multiple parameters jQuery sends, and which
// can be important.
//
// Here is a function which builds a jQuery AJAX promise, then turns it into a Q promise while correctly processing
// jQuery's error information.
//
// It calls a function called interpretAJAXError which takes jQuery's jqXHR, textStatus, errorThrown parameters
// (see http://api.jquery.com/jQuery.ajax/, under 'error') and turns it into a single value. This function can be
// arbitrarily complex, looking at all parameters, custom messages, etc.

function buildAJAXPromise(_options) {
    var jQueryPromise = $.ajax(Object.assign({}, {
        dataType: 'json',
        timeout: 3000,
    }, _options));

    // Copy of Q's coerce (https://github.com/kriskowal/q/blob/v1/q.js#L1185)
    // We intercept the error parameters, collect them, then send them on to Q's deferred.
    var deferred = Q.defer();
    Q.nextTick(function () {
        try {
            jQueryPromise.then(
                deferred.resolve,
                function(jqXHR, textStatus, errorThrown) {
                    return deferred.reject(interpretAJAXError(jqXHR, textStatus, errorThrown));
                },
                deferred.notify
            );
        } catch (exception) {
            deferred.reject(exception);
        }
    });
    return deferred.promise;
}