Adding a directory to sys.path with pathlib

you need to append the path as a string to sys.path:

PROJECT_DIR = Path(__file__).parents[2]
sys.path.append(
    str(PROJECT_DIR / 'apps')
)

PROJECT_DIR is instance of PosixPath which has all the goodies like / and parents etc. but you need to convert it to a regular string if you want to use is somewhere a string is expected - like sys.path.

Support for path-like-objects on sys.path is coming (see this pull request) but not here yet.