Include cache dir in local counterpart of URIs

Include cache dir in local counterpart of URIs

Before:

- URI: https://a.b.c/d/e.xml
- Local path: https/a.b.c/d/e.xml

Now:

- URI: https://a.b.c/d/e.xml
- Local path: /path/to/cache/https/a.b.c/d/e.xml

Is a bit more memory-gluttonous, but prints a more helpful string,
and simplifies user code by taking care of the task up front.