In Rails, `ActionDispatch::Http::UploadedFile` has an accessor to access a `Tempfile` object. However, `Rack::Test::UploadedFile` does not provide that, but provinding the `#path` method instead. To be able to support both, we have to check for existance for `#tempfile` method, then fallback to `#path` method. Fixes #807
It's not working correctly as expected, so let's revert this for now. This reverts commit 51bb0f9.
Needs work for S3 Attachments.