def create_default_groups(self):
        for group in self.groups:
            group = group.replace(" ", "_").lower()
            self[group] = NamedRequirements(group)
def trapped_signals(cls, new_signal_handler):
        """A contextmanager which temporarily overrides signal handling.

        NB: This method calls signal.signal(), which will crash if not called from the main thread!
        """
        previous_signal_handler = cls.reset_signal_handler(new_signal_handler)
        try:
            yield
        finally:
            cls.reset_signal_handler(previous_signal_handler)