gh-139322: Reenable test_os.test_getlogin() (#139498)

Fix also getlogin() errno.

Lib/test/test_os/test_os.py

@@ -3197,13 +3197,16 @@ def test_spawnvpe_invalid_env(self):
         self._test_invalid_env(os.spawnvpe)
 
 
-# The introduction of this TestCase caused at least two different errors on
-# *nix buildbots. Temporarily skip this to let the buildbots move along.
-@unittest.skip("Skip due to platform/environment differences on *NIX buildbots")
 @unittest.skipUnless(hasattr(os, 'getlogin'), "test needs os.getlogin")
 class LoginTests(unittest.TestCase):
     def test_getlogin(self):
-        user_name = os.getlogin()
+        try:
+            user_name = os.getlogin()
+        except OSError as exc:
+            if exc.errno in (errno.ENOTTY, errno.ENXIO):
+                self.skipTest(str(exc))
+            else:
+                raise
         self.assertNotEqual(len(user_name), 0)
 
 

Misc/NEWS.d/next/Library/2025-10-02-15-45-08.gh-issue-139322.rouPGj.rst

@@ -0,0 +1,2 @@
+Fix :func:`os.getlogin` error handling: fix the error number. Patch by
+Victor Stinner.

Modules/posixmodule.c

@@ -9605,7 +9605,7 @@ os_getlogin_impl(PyObject *module)
     int err = getlogin_r(name, sizeof(name));
     if (err) {
         int old_errno = errno;
-        errno = -err;
+        errno = err;
         posix_error();
         errno = old_errno;
     }