Python "NotADirectoryError: [Errno 20]" in CI

NotADirectoryError: [Errno 20] Not a directory is raised when an operation expects a directory in a path but finds a regular file there, for example listing or traversing through a file.

What this error means

A step fails with "NotADirectoryError: [Errno 20] Not a directory: 'archive.zip/inner'" while listing or joining a path.

python

NotADirectoryError: [Errno 20] Not a directory: 'data.tar/contents'

Common causes

Treating an archive or file as a directory

Code appended a child path to something that is a file (a tar/zip), so traversal fails.

A name collision where a dir was expected

A previous step wrote a file with the same name the code now tries to enter as a folder.

How to fix it

Verify the path is a directory before traversing

Check path.is_dir() before listing or joining child names.
For archives, extract to a temp directory and traverse the extraction.
Resolve name collisions so directories and files do not share a name.

Python

import pathlib
p = pathlib.Path(target)
if not p.is_dir():
    raise NotADirectoryError(f"expected a directory: {p}")

How to prevent it

Check is_dir() before directory operations.
Extract archives before traversing their contents.
Avoid file/dir name collisions in build output.