def safe_join(base, *paths):
    """
    A version of django.utils._os.safe_join for S3 paths.

    Joins one or more path components to the base path component
    intelligently. Returns a normalized version of the final path.

    The final path must be located inside of the base path component
    (otherwise a ValueError is raised).

    Paths outside the base path indicate a possible security
    sensitive operation.
    """
    base_path = force_text(base)
    base_path = base_path.rstrip('/')
    paths = [force_text(p) for p in paths]

    final_path = base_path
    for path in paths:
        final_path = urlparse.urljoin(final_path.rstrip('/') + "/", path)

    # Ensure final_path starts with base_path and that the next character after
    # the final path is '/' (or nothing, in which case final_path must be
    # equal to base_path).
    base_path_len = len(base_path)
    if (not final_path.startswith(base_path) or
            ('', '/') not in final_path[base_path_len:base_path_len + 1]):
        raise ValueError('the joined path is located outside of the base path'
                         ' component')

    return final_path.lstrip('/')
dataset/ETHPy150Open jschneier/django-storages/storages/backends/s3boto.py/safe_join/swapped operands of `not in`