Return a bool telling whether or ``path`` is absolute. If ``path`` is None,
    return ``True``. This function is designed to validate variables which
    optionally contain a file path.

def _path_is_abs(path):
    '''
    Return a bool telling whether or ``path`` is absolute. If ``path`` is None,
    return ``True``. This function is designed to validate variables which
    optionally contain a file path.
    '''
    if path is None:
        return True
    try:
        return os.path.isabs(path)
    except AttributeError:
        # Non-string data passed
        return False