def __init__(self, *args, **kwargs):
        """
        Save the original SIGINT handler for later.
        """
        super(InterruptibleMixin, self).__init__(*args, **kwargs)

        self.original_handler = signal(SIGINT, self.handle_sigint)

        # If signal() returns None, the previous handler was not installed from
        # Python, and we cannot restore it. This probably should not happen,
        # but if it does, we must restore something sensible instead, at least.
        # The least bad option should be Python's default SIGINT handler, which
        # just raises KeyboardInterrupt.
        if self.original_handler is None:
            self.original_handler = default_int_handler

        Save the original SIGINT handler for later.
        
stackoverflow/venv/lib/python3.6/site-packages/pip-19.0.3-py3.6.egg/pip/_internal/utils/ui.py