Can you change this to use a tempdir?  Then we don't have to cleanup in the ensure.  e.g.:

```
irb(main):001:0> require 'tempfile'
=> true
irb(main):002:0> Dir.tmpdir
=> "/var/folders/yv/c2r06v597n5bdpw_bf8qcmb80000gp/T"
irb(main):003:0>
```