You're including multiple sentences here.  However, I believe `RSpec.deprecate` will put this into its formatted sentence, which will look funny.  Would be good to see what the full deprecation warning actually is, and correct this appropriately with something like:

``` ruby
RSpec.deprecate("The host argument to to `RSpec::Mocks.setup`", :replacement => "include `RSpec::Mocks::ExampleMethods` in #{host.inspect}")
```

I _think_ that will read well, but I haven't looked at the formatting in a while so please confirm.