Fix: cache_dir.mkdir is causing issue when cache_dir is readonly

[youkefan18]

When deploying application in production, there would be cases where models are pre-downloaded and mounted as read only folder for image to use.

This pull request checks if cache_dir already exists before trying to 'mkdir' to avoid permission issue.

[joein]

Hey @youkefan18

I tried to reproduce the issue with the current code

I did the following

mkdir qwerty
chmod 555 qwerty

from pathlib import Path
Path('qwerty').mkdir(parents=True, exist_ok=True)

No error was risen
Are you sure that cache_dir actually exists?

[joein]

Hey @youkefan18

Is this still relevant for you?