With PEP 479, the behaviour of StopIteration is changing. Raising it to stop a generator is considered incorrect and from Python 3.7 this will cause a RuntimeError. The PEP recommends using the return statement. More details: https://www.python.org/dev/peps/pep-0479/#examples-of-breakage Change-Id: Ia067940066a5666926dcf61136b03d721a87666e