Fix the new test on Windows

subprocess only resolves a relative executable against its cwd argument
on POSIX, so the test failed with FileNotFoundError on Windows. Change
directory in the test process instead.

Author: Gronoxx

Lib/test/test_venv.py

@@ -23,8 +23,8 @@
                           is_wasm32,
                           requires_venv_with_pip, TEST_HOME_DIR,
                           requires_resource, copy_python_src_ignore)
-from test.support.os_helper import (can_symlink, EnvironmentVarGuard, rmtree,
-                                    TESTFN, FakePath)
+from test.support.os_helper import (can_symlink, change_cwd, EnvironmentVarGuard,
+                                    rmtree, TESTFN, FakePath)
 import unittest
 import venv
 from unittest.mock import patch, Mock
@@ -318,11 +318,14 @@ def test_prefixes_with_non_normalised_executable(self):
         self.addCleanup(rmtree, subdir)
         relative_exe = os.path.join(
             os.pardir, os.path.basename(self.env_dir), self.bindir, self.exe)
-        p = subprocess.run(
-            [relative_exe, '-c',
-             'import sys; print(sys.prefix); print(sys.exec_prefix)'],
-            cwd=subdir, capture_output=True, encoding='utf-8',
-            env={**os.environ, 'PYTHONHOME': ''})
+        # Windows does not resolve a relative executable against subprocess's
+        # cwd argument, so change directory in this process instead.
+        with change_cwd(subdir):
+            p = subprocess.run(
+                [relative_exe, '-c',
+                 'import sys; print(sys.prefix); print(sys.exec_prefix)'],
+                capture_output=True, encoding='utf-8',
+                env={**os.environ, 'PYTHONHOME': ''})
         self.assertEqual(p.returncode, 0, p.stderr)
         self.assertNotIn('Unexpected value in sys.prefix', p.stderr)
         self.assertNotIn('Unexpected value in sys.exec_prefix', p.stderr)