This is needed to fix crashing tests with newer versions of Python. It seems to apply cleanly for me.
lit googletest.py: Don't raise StopIteration in generator
The intention here seems to be to end the generator function, but with
modern Python, raising StopIteration causes a runtime error
(https://www.python.org/dev/peps/pep-0479/).
Differential revision: https://reviews.llvm.org/D79169