iirc The scheme is needed because FilterFileSystem doesn't implement getScheme, so in any case we dont have support for it.  Specificlaly the testMkdirsWithUMask will fail without getScheme for accidental reasons (i.e. there is a little if statement in the published test which checks if scheme is s3).  But in any case, getScheme should be implemented i would think...  Probably we should have a more direct test of it .