stringify errors. http://stackoverflow.com/questions/18391212/is-it-not-possible-to-stringify-an-error-using-json-stringify

gistfile1.txt

Object.defineProperty(Error.prototype, 'toJSON', {
    value: function () {
        var alt = {};

        Object.getOwnPropertyNames(this).forEach(function (key) {
            alt[key] = this[key];
        }, this);

        return alt;
    },
    configurable: true
});
var error = new Error('testing');
error.detail = 'foo bar';

console.log(JSON.stringify(error));
// {"message":"testing","detail":"foo bar"}