Auth Exception

You can handle the exceptions manually: https://spatie.be/docs/laravel-permission/v5/advanced-usage/exceptions

make sure your request says that it wants a json response.

There is a repo with laravel tips that shows how to force a json response by adding the header to incomming requests:

public function handle($request, Closure $next)
{
    $request->headers->set('Accept', 'application/json');
    return $next($request);
}

You can use something like this to all the api routes, so you don't get the HTML page error, just a json with the error.

Source to the tip: https://github.com/LaravelDaily/laravel-tips/blob/master/api.md#force-json-response-for-api-requests