Fake writer (to devnull).

devnull.py

class DevNull:
    """Pretends to write but doesn't."""

    def write(self, msg):
        pass

    def flush(self):
        pass

    def close(self):
        pass

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_value, traceback):
        self.close()