Rails 6 test issue

```
An error occurred in a `before(:suite)` hook.
Failure/Error: ThinkingSphinx::Test.start_with_autostop

Riddle::CommandFailedError:
  Sphinx command failed to execute
 ```

I'm seeing this after our Rails 6 upgrade. I'm wondering if this deprecation warning finally turned into an error?

https://github.com/pat/thinking-sphinx/issues/1165
