Line 522 in test file Lib/test/test_pep380.py says:

                trace.append("Should not have yielded:", y)

However, 'trace' is a list and list.append() only takes one parameter, so this should read:

                trace.append("Should not have yielded: %r" % y)

I noticed it because Cython's type analysis refuses to compile this. This line is just a failure guard and is never reached in the normal test execution, that's why it doesn't show in CPython's test runs.