After https://github.com/python/cpython/commit/0b858cdd5d114f0890b11b6c4d6559d0ceb468ab
(bpo-1635741: Convert _multibytecodec to multi-phase init),

On Windows x64/x86 with chinese/japanese/korean system-locale,
MultibyteCodec_Check() in multibytecodec.c returns false and
PyExc_TypeError follows. This affects some tests and PGO training.



1) python -m test --verbose test_threading

======================================================================
FAIL: test_daemon_threads_fatal_error (test.test_threading.SubinterpThreadi
ngTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\cpython-0b858\lib\test\test_threading.py", line 1124, in test_da
emon_threads_fatal_error
    self.assertIn("Fatal Python error: Py_EndInterpreter: "
AssertionError: 'Fatal Python error: Py_EndInterpreter: not the last thread
' not found in 'TypeError: codec is unexpected type\nFatal Python error: _P
yThreadState_Delete: tstate 00000000003FF980 is still current\nPython runti
me state: initialized\n\nThread 0x00000710 (most recent call first):\n<no P
ython frame>\n'



2) python -m test --verbose test_embed

======================================================================
FAIL: test_audit_subinterpreter (test.test_embed.AuditingTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\cpython-0b858\lib\test\test_embed.py", line 1433, in test_audit_
subinterpreter
    self.run_embedded_interpreter("test_audit_subinterpreter")
  File "C:\cpython-0b858\lib\test\test_embed.py", line 104, in run_embedded
_interpreter
    self.assertEqual(p.returncode, returncode,
AssertionError: 3221225477 != 0 : bad returncode 3221225477, stderr is 'Typ
eError: codec is unexpected type\nFatal Python error: _PyThreadState_Delete
: tstate 000000000050CAF0 is still current\nPython runtime state: initializ
ed\n\nThread 0x000009d8 (most recent call first):\n<no Python frame>\n'

======================================================================
FAIL: test_subinterps_different_ids (test.test_embed.EmbeddingTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\cpython-0b858\lib\test\test_embed.py", line 169, in test_subinte
rps_different_ids
    for run in self.run_repeated_init_and_subinterpreters():
  File "C:\cpython-0b858\lib\test\test_embed.py", line 110, in run_repeated
_init_and_subinterpreters
    out, err = self.run_embedded_interpreter("test_repeated_init_and_subint
erpreters")
  File "C:\cpython-0b858\lib\test\test_embed.py", line 104, in run_embedded
_interpreter
    self.assertEqual(p.returncode, returncode,
AssertionError: 3221225477 != 0 : bad returncode 3221225477, stderr is 'Typ
eError: codec is unexpected type\nFatal Python error: _PyThreadState_Delete
: tstate 000000000041C960 is still current\nPython runtime state: initializ
ed\n\nThread 0x00000a40 (most recent call first):\n<no Python frame>\n'

======================================================================
FAIL: test_subinterps_distinct_state (test.test_embed.EmbeddingTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\cpython-0b858\lib\test\test_embed.py", line 177, in test_subinte
rps_distinct_state
    for run in self.run_repeated_init_and_subinterpreters():
  File "C:\cpython-0b858\lib\test\test_embed.py", line 110, in run_repeated
_init_and_subinterpreters
    out, err = self.run_embedded_interpreter("test_repeated_init_and_subint
erpreters")
  File "C:\cpython-0b858\lib\test\test_embed.py", line 104, in run_embedded
_interpreter
    self.assertEqual(p.returncode, returncode,
AssertionError: 3221225477 != 0 : bad returncode 3221225477, stderr is 'Typ
eError: codec is unexpected type\nFatal Python error: _PyThreadState_Delete
: tstate 000000000047C960 is still current\nPython runtime state: initializ
ed\n\nThread 0x00000b34 (most recent call first):\n<no Python frame>\n'

======================================================================
FAIL: test_subinterps_main (test.test_embed.EmbeddingTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\cpython-0b858\lib\test\test_embed.py", line 163, in test_subinte
rps_main
    for run in self.run_repeated_init_and_subinterpreters():
  File "C:\cpython-0b858\lib\test\test_embed.py", line 110, in run_repeated
_init_and_subinterpreters
    out, err = self.run_embedded_interpreter("test_repeated_init_and_subint
erpreters")
  File "C:\cpython-0b858\lib\test\test_embed.py", line 104, in run_embedded
_interpreter
    self.assertEqual(p.returncode, returncode,
AssertionError: 3221225477 != 0 : bad returncode 3221225477, stderr is 'Typ
eError: codec is unexpected type\nFatal Python error: _PyThreadState_Delete
: tstate 000000000032C960 is still current\nPython runtime state: initializ
ed\n\nThread 0x00000bf0 (most recent call first):\n<no Python frame>\n'