This code runs in the context of testing, so it's fine (and actually useful) to be a bit verbose to help with debugging.
E.g. you should print the file name here if you failed to remove it.

Same here, you should print something like "Starting test_runner for <script name>" before calling the command

Please use some less generic environment variable name here, there is a high risk of collision. E.g. CHRONIK_CLIENT_RUST_IPC_SOCKET

I don't think you need to pass this, it's already determined by the test_runner.py. This will also avoid a copy because you can remove the above clone()

Let's bump the timeout to something absurdly large.
You don't want the test to fail randomly because the machine running it is slow. OTOH it's fine to wait say 1 minute if there is a real error.

This is unreachable due to the above assert

I still don't get it. If you expect result to be Ok(), what's the point of the above check against Err() ?

You should return an error here. For now if the timeout is reached cargo will report no error !