gh-104522: Fix test_subprocess failure when build Python in the root …

…home directory (GH-114236)

* gh-104522: Fix test_subprocess failure when build Python in the root home directory

EPERM is raised when setreuid() fails.
EACCES is set in execve() when the test user has not access to sys.executable.

Lib/test/test_subprocess.py

@@ -1991,9 +1991,9 @@ def test_process_group_0(self):
 
     @unittest.skipUnless(hasattr(os, 'setreuid'), 'no setreuid on platform')
     def test_user(self):
-        # For code coverage of the user parameter.  We don't care if we get an
-        # EPERM error from it depending on the test execution environment, that
-        # still indicates that it was called.
+        # For code coverage of the user parameter.  We don't care if we get a
+        # permission error from it depending on the test execution environment,
+        # that still indicates that it was called.
 
         uid = os.geteuid()
         test_users = [65534 if uid != 65534 else 65533, uid]
@@ -2018,11 +2018,10 @@ def test_user(self):
                                 user=user,
                                 close_fds=close_fds)
                     except PermissionError as e:  # (EACCES, EPERM)
-                        self.assertIsNone(e.filename)
-                    except OSError as e:
-                        if e.errno not in (errno.EACCES, errno.EPERM):
-                            raise
-                        self.assertIsNone(e.filename)
+                        if e.errno == errno.EACCES:
+                            self.assertEqual(e.filename, sys.executable)
+                        else:
+                            self.assertIsNone(e.filename)
                     else:
                         if isinstance(user, str):
                             user_uid = pwd.getpwnam(user).pw_uid