I'm working on `uvll::write()` since it also blocks win32 tests.
I guess most code using this pattern:
```Rust
do scheduler.deschedule_running_task_and_then |_, task| {
    do call_uv_something_with_callback |_watcher, status| {
        let scheduler: ~Scheduler = Local::take();
        scheduler.resume_blocked_task_immediately(task_cell.take());
    }
}
```
can be problematic if `call_uv_something_with_callback()` is not aware of `uv_something() != 0`.