I traced the commits and seems like this is here to support custom splatting (`status, header, _ = a_response`), so  we can't just remove it. Looking at rspec/rspec-expectations#166 and rack/rack#419, it seems like the issue is that the return value of `to_ary` should not contain `self`. Is it possible to fix this in a similar fashion as https://github.com/rack/rack/commit/5b251a986962f3577e14c01a698fab9dd21383ba instead?