Victor,
As you explain in your own documentation, the proposed method is equivalent to ``(time.mktime(self.timetuple()), self.microsecond)``, so all it does is replacing a less than a one-liner. Moreover, I am not sure time.mktime(self.timetuple()) is something that people would want to do with a TZ-aware datetime. If the tzinfo of the datetime object does not match the system TZ used by mktime, the result will be quite misleading.
On the patch itself:
1. See my comment at Issue1726687 about the tm_wday == 1 typo.
2. I don't think time_t to long cast is safe on all platforms.