Tests fail but gulp returns 0

I'm not sure if this is a gulp-qunit problem, a gulp problem, or I'm holding it wrong. :-)

My gulpfile is pretty standard:
```
var gulp = require('gulp');
var qunit = require('gulp-qunit');

gulp.task('test', () => {
return gulp.src('./test.html').pipe(qunit());
});
```

I'm using gulp 4.0.1, gulp-qunit 2.0.2. If I run my tests, and the tests pass, then gulp returns 0. But if I edit my tests to force them to fail:

```
$ gulp test
...
[13:46:51] Took 75ms to run 203 tests. 202 passed, 1 failed.
[13:46:51] gulp-qunit: ✖ QUnit assertions failed in test.html

$ echo $?
0
```

`gulp test` still returns zero? How do I get gulp to return something else if the tests fail?