Implement 3.7 feature signal.set_wakeup_fd(warn_on_full_buffer=False)
The flag warn_on_full_buffer flag to set_wakeup_fd was added in Python 3.7:
https://docs.python.org/3/library/signal.html#signal.set_wakeup_fd
The main user I know of right now is trio: https://github.com/python-trio/trio/issues/109