./python Lib/unittest/test/testmock/testmock.py ..........................................s..................................... ---------------------------------------------------------------------- Ran 80 tests in 0.180s OK (skipped=1) So thats great. I am going to have to stare that this quite hard to be sure I understand why it fails without the change away from 'for line in ' - but yes, this is the right place, and I'll commit it to 3.5 and 3.6 and backport it to the external mock tomorrow. Thanks!