It looks like you’re still running in a chroot, so no need for an explicit tmpdir. It already runs in a tmpdir.

PEX_EXTRA_SYS_PATH

can be relative; you don’t need the absolute path of the tmpdir. You’re calling

await Get(PythonSources, PythonSourcesRequest)

already. That’s good. That’s what you want. Now, next step is to likely add this line:

env = {"PEX_EXTRA_SYS_PATH": ":".join(prepared_sources.source_roots)}

(https://github.com/pantsbuild/pants/blob/9dc89b69d075892605a50fe1aac107bcd0bef3ee/src/python/pants/backend/python/goals/pytest_runner.py#L231) This will append the source roots to the

$PYTHONPATH

. For example, if you have code at

src/python/project/app.py

, then this will add

src/python

to

$PYTHONPATH

, which allows Python processes to import the module

<http://project.app|project.app>

, rather than

<http://src.python.project.app|src.python.project.app>