gh-131290: fix direct test files invocation

[MaximGit1]

Now tests are launched via ./python.exe and work correctly

• Issue: Multiple tests failing when invoked directly via ./python Lib/test/... #131290

[cpython-cla-bot]

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[picnixz]

Which test is failing because of the lack of __spec__?

[MaximGit1]

test_others

user\cpython\Lib\test\test_pyclbr.py", line 226, in test_others
    cm(
    ~~^
        'pdb',
        ^^^^^^
        # pyclbr does not handle elegantly `typing` or properties
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        ignore=('Union', '_ModuleTarget', '_ScriptTarget', '_ZipTarget', 'curframe_locals'),
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
 File "user\cpython\Lib\test\test_pyclbr.py", line 142, in checkModule
    self.assertHaskey(dict, name, ignore)
    ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^
  File "user\cpython\Lib\test\test_pyclbr.py", line 39, in assertHaskey
    self.assertIn(key, obj)
    ~~~~~~~~~~~~~^^^^^^^^^^
AssertionError: 'Pdb' not found in {'contextmanager': <pyclbr.Function object at 0x000001DA2A910690>}

----------------------------------------------------------------------
Ran 6 tests in 11.022s

FAILED (failures=1, errors=1)

[picnixz]

Suggested change

	os.environ['PYTHONREGRTEST_UNICODE_GUARD'] = 'some_value' # for test_unicode_guard_env
	unittest.main()
	with EnvironmentVarGuard() as env:
	# for test_unicode_guard_env
	PYTHONREGRTEST_UNICODE_GUARD = "some_value"
	unittest.main()

and add some from test.support.os_hepler import EnvironmentVarGuard top-level import. However, I don't know if this is correct to test test_unicode_guard_env like this or if we shouldn't just skip if it we're running it from __main__. Namely, decorate the test with @unittest.skipIf(__name__ == '__main__') cc @vstinner

[picnixz]

• The CLA needs to be signed.
• The NEWS entry seems to fail but I don't know if it's because of its name or if it's because of its content.

[vstinner]

For regrtest, I would prefer this fix:

diff --git a/Lib/test/test_regrtest.py b/Lib/test/test_regrtest.py
index 510c8f69631..7e317d5ab94 100644
--- a/Lib/test/test_regrtest.py
+++ b/Lib/test/test_regrtest.py
@@ -2546,4 +2546,5 @@ def test_test_result_get_state(self):
 
 
 if __name__ == '__main__':
+    setup.setup_process()
     unittest.main()