Repeats func(...) call until something other than None is returned.

def _repeat(func):
    """Repeats func(...) call until something other than None is returned."""
    @functools.wraps(func)
    def wrapper(*args, **kwargs):
        """Repeats the call until True is returned."""
        ret = None
        while ret is None:
            ret = func(*args, **kwargs)
        return ret
    return wrapper