How can we override reject creating a new Error Object?

https://github.com/sinonjs/sinon/blob/4310343393b16b92b56526ab4614da4eb2886efa/lib/sinon/default-behaviors.js#L176

I'm maintaining some code that rejects strings and this is creating issues while testing. my bluebird catches are not behaving correctly.

bluebird.rejects('Something')
    .catch(e => e === 'Something' /* true */, () => console.log(typeof e) /*string*/)
    .catch(() => console.log('should not be here'));

However using sinon.stub().usingPromise('bluebird').rejects('Something'); ends up creating an error object with the name Something. Not expected at all.

Before someone says we are only supporting native Promises, let's investigate what they do!

Promise.reject('Something')
     .catch(e => {
        console.log(e === 'Something'); // true
        console.log(typeof e); // string
    });

Hmmm, they don't create an Error class, they just toss the exception it was given like a throw.

try { 
    throw 'Something'; 
} catch (e) { 
    console.log(e === 'Something');  // true
    console.log(typeof e); // string
}

Start at lib/sinon/default-behaviors.js#L176 and trace how rejects handles the supplied value when using a configured promise implementation. Compare that behavior with the native Promise.reject and Bluebird examples in the issue; done means a rejected string remains the original string rather than becoming an Error object, with regression coverage for the behavior.