In Differ, an array will have `PP.pp` called on it from this line: https://github.com/rspec/rspec-support/blob/master/lib/rspec/support/differ.rb#L182

That output looks like: 

```
> PP.pp(["poo", "car"], "")
 => "[\"poo\", \"car\"]\n" 
```

... so it has a trailing newline, and trailing newlines are not being ignored anymore.