I tracked it down: https://www.youtube.com/watch?v=QrrH2lcl9ew

I don't think it was on-device code, as they talked about porting Python projects. But you can watch the talk to see if I'm misremembering.

Thanks!

In the transcript I found more talk about porting C++ and Go to Rust, without Python rewrite references... still interesting tidbits, like

"when we've rewritten systems from go into rust we've found that it takes about the same size team about the same amount of time to build it that is there's no loss in productivity when moving from go to rust "