Hi!
If for some reason you need python backdoors then veil is not an option, as mentioned their developers are the ones who need to fix such issue. In any case for the course there’s no need to use python backdoors, the other languages used by veil will work just fine.
As mentioned earlier we need to solve one issue at a time, you decided to begin with veil. So, as I said before using other languages will be fine, if you need python backdoors for some specific reason then google for an alternative tool (I personally don’t like python for backdoors so can’t really suggest any tool). Or we can keep going on using a different payload language with veil.

Also, the screenshots don’t have view permissions, remember to allow it for anyone who has the link.

Greetings!
Diego