Log Message:
py-nihtest: update to 1.9.1.

Fix self tests inside pkgsrc.

# 1.9.1 [2024-12-17]

- Fix directory comparators broken in 1.9.0.
- Fix handling of files in nested directories.
- Fix on Windows.

# 1.9.0 [2024-12-17]

- Fail for unexpeced empty directories.
- Allow specifying existance of directories.
- Check for duplicate file/directory specifications in test case.
- Deprecate `mkdir` directive, use `directory` instead.