Go back to stricter tear down, enforcing expected_returncode

Author: JamesParrott

tests/lib/conftest.py

@@ -79,9 +79,9 @@ def starter(name: str, expected_returncode: int = 0) -> None:
 
         def fin():
             stop_process(proc)
-            # Return code can be None on Python 3.8
+            # If return code is None, process has not stopped.
             # https://docs.python.org/library/subprocess.html#subprocess.Popen.returncode
-            if proc.returncode is not None and proc.returncode != expected_returncode:
+            if proc.returncode != expected_returncode:
                 raise RuntimeError(f"Client {name} exited with code {proc.returncode}, expected {expected_returncode}")
 
         request.addfinalizer(fin)