python-setup: Fix site-package selection for unix

python-setup/find_site_packages.py

@@ -19,12 +19,16 @@
     # poetry/requests-3, I was not allowed to install pip! So I did not pursue this
     # option further.
     #
-    # Instead, testing (on both Windows and Linux) shows that the last entry of
-    # `site.getsitepackages()` has the right path (note: On linux there is only a single
-    # entry), whereas `site.getusersitepackages()` is about the system python (very
-    # confusing).
+    # Instead, testing `site.getsitepackages()` contains has the right path, whereas
+    # `site.getusersitepackages()` is about the system python (very confusing).
     #
     # We can't use the environment variable POETRY_VIRTUALENVS_OPTIONS_NO_PIP because it
     # does not work, see https://github.com/python-poetry/poetry/issues/5906
     import site
-    print(site.getsitepackages()[-1])
+
+    if sys.platform.startswith("win32"):
+        # On windows, the last entry of `site.getsitepackages()` has the right path
+        print(site.getsitepackages()[-1])
+    else:
+        # on unix, the first entry of `site.getsitepackages()` has the right path
+        print(site.getsitepackages()[0])