Refactoring to:

```
from compat import LocalFilesystem

class BrinkFilesystem(LocalFilesystem):
```

will get rid of the separate test. I took a quick look at the specifics of `BrinkFilesystem` and decided that it would be to harrowing a task for the purpose of this ticket.

Please let me know if this is not ok with you and/or if you think it's something we should consider in the future and I'll create a ticket.

Thanks!