Rajoute `sleep(2)` pour gérer l'éventuelle absence de microsecondes

D'après [la doc python](https://docs.python.org/2/library/datetime.html#datetime.datetime.now) : 

> Return the current local date and time. If optional argument tz is None or not specified, this is like today(), but, ***if possible***, supplies more precision than can be gotten from going through a time.time() timestamp (for example, this may be possible on platforms supplying the C gettimeofday() function).