Debugging file upload issues

file.js

({

        /* File: ./custom/clients/base/fields/file/file.js */

        extendsFrom: 'FileField',

        _doValidateFileError: function(fields, errors, callback, resp) {
                app.alert.dismiss('upload');

                app.logger.fatal(resp);

                var errors = errors || {},
                        fieldName = this.name;
                        errors[fieldName] = {};

                switch (resp.error) {
                        case 'request_too_large':
                                errors[fieldName].tooBig = true;
                                break;
                        default:
                                errors[fieldName].uploadFailed = true;
                }

                this.model.unset(fieldName + '_guid');
                callback(null, fields, errors);
        }
})