> What do you mean? signal.SIGPOLL exists in Python 3.3.

Right, si_band added.

> - test_sigwaitinfo(), test_sigtimedwait_poll(), test_sigwaitinfo_interrupted() are called from a child process. In test_wait(), I chose to write manually to stdout and call os._exit(1) (oh, I forgot an explicit sys.stdout.flush()). I don't know if you can use TestCase methods in a child process (I don't know what is written to stdout, _wait_helper() calls os._exit).

I assume you mean stderr? Well anyway if the assert* fails, an exception is raised and then caught by this code in wait_helper():
"""
except BaseException as err:
                print("error: {}".format(err), file=sys.stderr)
                sys.stderr.flush()
                os._exit(1)
"""
which prints it to stderr.
If this is OK, I'll commit the patch.