fix(env): always include userbase in paths

When executing Python in isolated (-I) mode, user site is disabled. This
should not exclude userbase from generated paths.

src/poetry/utils/env/base_env.py

@@ -338,6 +338,13 @@ def run_pip(self, *args: str, **kwargs: Any) -> str:
         return self._run(cmd, **kwargs)
 
     def run_python_script(self, content: str, **kwargs: Any) -> str:
+        # Options Used:
+        #     -I        : Run Python in isolated mode. (#6627)
+        #     -W ignore : Suppress warnings.
+        #
+        # TODO: Consider replacing (-I) with (-EP) once support for managing Python <3.11 environments dropped.
+        # This is useful to prevent user site being disabled over zealously.
+
         return self.run(
             self._executable,
             "-I",

src/poetry/utils/env/script_strings.py

@@ -104,7 +104,8 @@ def _version_nodot(version):
 
 if site.check_enableusersite():
     paths["usersite"] = site.getusersitepackages()
-    paths["userbase"] = site.getuserbase()
+
+paths["userbase"] = site.getuserbase()
 
 print(json.dumps(paths))
 """