Martin von Zweigbergk <martinvonz@google.com> [Thu, 11 Jul 2019 15:30:43 -0700] rev 4755
py3: fix progress() functions to not use "%s" with int
Python3 doesn't support "%s" with int arguments (and not with None
arguments either, which this code was also using).
Martin von Zweigbergk <martinvonz@google.com> [Wed, 17 Jul 2019 11:45:37 -0700] rev 4754
py3: make random topic name generation consistent across py2/py3
random.choice() (and others based on random.randint()) changed between
py2 and py3 without a way to get the py2 behavior. However,
random.random() did not change, so we can re-implement random.choice()
based on that.