Python 3.7 made async a reserved word, which broke the widely used celery package up until their most recent release.

Raising a StopIterationErorr in a generator in 3.7 now raises instead of ending the iteration, which broke several functions at my workplace.

3.8 has several further backwards incompatible changes incoming: https://docs.python.org/3.8/whatsnew/3.8.html#changes-in-pyt...