He was taken on by Rennes to cover their regular right back who I think was/is also their captain who was out injured. He played some games until the regular right back was fit again. He earned some good reviews at first.
I don't know whether Spence will turn out any good, time will tell. I don't blame Conte for not trying him although I did find it strange he didn't get more of a look in considering at the time Conte didn't seem to know who he wanted to play at right back.
It was Conte who labelled Spence a 'club signing', indicating he didn't really want him. And this is where I do blame Conte. You work with what you have and as a manager he should be good enough to get something out of the players in front of him. Effectively publically trashing Spence, Danjuma and I think Gil as 'club signings' he didn't want or approve is not helpful to anyone - the players or the club - all of whom will be around far longer than Conte was ever going to last.
Conte gets the blame because he acted like a petulant little shit who had a tantrum when he wasn't getting his own way.