A quick eyeball of the test doesn't reveal anything obvious:

- if the subprocess is failing, it is doing so in such a way that it is still returning a 0 error code and isn't writing anything to stdout (as those assertions are before the check that the expected compiled file exists)
- the invocation of script_helper looks sensible
- if the directory creation fails, it won't get as far as running the subprocess

To instrument this, I would suggest starting by adding an assertion message on the failing assertion that includes "fn". My guess is that with the random directory name in there, the regex is triggering on the directory name and hence excluding the __init__.py file as well.