HystrixCommand returning Observable

UserService.kt

//...elided code...//
@HystrixCommand(/* ...some very advanced hystrix configurations here... */)
open fun fetchUser(email: String): Observable<User> {
    // MUST return ObservableResult when using @HystrixCommand and Observable<T>
    // See: https://github.com/Netflix/Hystrix/issues/729
    return object : ObservableResult<User>() {
        override fun invoke() = client.fetchUser(email)
    }
}