Fix regession with sys.path filter (2)

Author: cdce8p

tests/test_self.py

@@ -931,7 +931,10 @@ def test_import_plugin_from_local_directory_if_pythonpath_cwd(tmpdir):
 
         with tmpdir.as_cwd():
             orig_pythonpath = os.environ.get("PYTHONPATH")
-            os.environ["PYTHONPATH"] = "."
+            if sys.platform == "win32":
+                os.environ["PYTHONPATH"] = "."
+            else:
+                os.environ["PYTHONPATH"] = f"{(orig_pythonpath or '').strip(':')}:."
             process = subprocess.run(
                 [
                     sys.executable,