Test `test_c_locale_coercion` fails on macos Sonoma

[sobolevn]

Repro: ./python.exe -m test test_c_locale_coercion -v

Short output:

======================================================================
FAIL: test_external_target_locale_configuration (test.test_c_locale_coercion.LocaleConfigurationTests.test_external_target_locale_configuration) (env_var='LC_CTYPE', configured_locale='UTF-8')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_c_locale_coercion.py", line 273, in test_external_target_locale_configuration
    self._check_child_encoding_details(var_dict,
  File "/Users/sobolev/Desktop/cpython/Lib/test/test_c_locale_coercion.py", line 230, in _check_child_encoding_details
    self.assertEqual(encoding_details, expected_details)
AssertionError: {'fse[36 chars]f-8:strict', 'stdout_info': 'utf-8:strict', 's[80 chars]: ''} != {'fse[36 chars]f-8:surrogateescape', 'stdout_info': 'utf-8:su[98 chars]: ''}
  {'fsencoding': 'utf-8',
   'lang': '',
   'lc_all': '',
   'lc_ctype': 'UTF-8',
   'stderr_info': 'utf-8:backslashreplace',
-  'stdin_info': 'utf-8:strict',
?                         ^^ ^

+  'stdin_info': 'utf-8:surrogateescape',
?                        ++++++ ^^^ ^^^

-  'stdout_info': 'utf-8:strict'}
?                          ^^ ^

+  'stdout_info': 'utf-8:surrogateescape'}
?                         ++++++ ^^^ ^^^


----------------------------------------------------------------------
Ran 7 tests in 0.883s

FAILED (failures=51)
test test_c_locale_coercion failed
test_c_locale_coercion failed (51 failures)

== Tests result: FAILURE ==

1 test failed:
    test_c_locale_coercion

Total duration: 924 ms
Total tests: run=7 failures=51
Total test files: run=1/1 failed=1
Result: FAILURE

Full output is attached below.
out.txt

Linked PRs

• gh-109989: Fix test_c_locale_coercion when PYTHONIOENCODING is set #113378
• [3.12] gh-109989: Fix test_c_locale_coercion when PYTHONIOENCODING is set (GH-113378) #113398
• [3.11] gh-109989: Fix test_c_locale_coercion when PYTHONIOENCODING is set (GH-113378) #113399

[ronaldoussoren]

The test passes for me, and AFAIC I get the same encodings in the headers as you (see details below). The only locale related environment variable is LC_CTYPE=UTF-8.

Details

== CPython 3.13.0a0 (heads/main-dirty:91fb8daa24, Sep 28 2023, 19:47:28) [Clang 15.0.0 (clang-1500.0.40.1)]
== macOS-14.0-arm64-arm-64bit little-endian
== Python build: debug
== cwd: /Users/ronald/Projects/Forks/cpython-upstream/build/build/test_python_worker_5207æ
== CPU count: 8
== encodings: locale=UTF-8, FS=utf-8
== resources: (all disabled, use -u option)

0:00:00 load avg: 2.71 Run 1 test sequentially
0:00:00 load avg: 2.71 [1/1] test_c_locale_coercion
AVAILABLE_TARGETS = ['UTF-8']
EXPECTED_C_LOCALE_EQUIVALENTS = ['C', 'invalid.ascii']
EXPECTED_C_LOCALE_STREAM_ENCODING = 'ascii'
EXPECTED_C_LOCALE_FS_ENCODING = 'utf-8'
EXPECT_COERCION_IN_DEFAULT_LOCALE = True
_C_UTF8_LOCALES = ('C.UTF-8', 'C.utf8', 'UTF-8')
_check_nl_langinfo_CODESET = False
test_LC_ALL_set_to_C (test.test_c_locale_coercion.LocaleCoercionTests.test_LC_ALL_set_to_C) ... ok
test_PYTHONCOERCECLOCALE_not_set (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_not_set) ... ok
test_PYTHONCOERCECLOCALE_not_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_not_zero) ... ok
test_PYTHONCOERCECLOCALE_set_to_one (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_one) ... skipped 'coerced LC_CTYPE locale: UTF-8'
test_PYTHONCOERCECLOCALE_set_to_warn (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_warn) ... ok
test_PYTHONCOERCECLOCALE_set_to_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_zero) ... ok
test_external_target_locale_configuration (test.test_c_locale_coercion.LocaleConfigurationTests.test_external_target_locale_configuration) ... ok

----------------------------------------------------------------------
Ran 7 tests in 0.927s

OK (skipped=1)

== Tests result: SUCCESS ==

[ronaldoussoren]

I checked again on main and I cannot reproduce (macOS 14.1.2 23B92 on an M1 MacBook).

@sobolevn : Is this something you can reproduce? Do you have PYTHONIOENCODING set in the environment?

BTW. I do get a lot of test errors when running with PYTHONIOENCODING set, see details below. One might argue that the test shouldn't fail when that environment variable is set.

Details

% PYTHONIOENCODING=UTF8:surrogateescape ./python.exe -m test test_c_locale_coercion -v
== CPython 3.13.0a2+ (heads/main-dirty:5aa317e4ca, Dec 5 2023, 11:57:35) [Clang 15.0.0 (clang-1500.1.0.2.5)]
== macOS-14.1.2-arm64-arm-64bit little-endian
== Python build: debug
== cwd: /Users/ronald/Projects/Forks/cpython-upstream/build/build/test_python_worker_12059æ
== CPU count: 8
== encodings: locale=UTF-8 FS=utf-8
== resources: all test resources are disabled, use -u option to unskip tests

Using random seed: 1055448953
Raised RLIMIT_NOFILE: 256 -> 1024
0:00:00 load avg: 3.02 Run 1 test sequentially
0:00:00 load avg: 3.02 [1/1] test_c_locale_coercion
AVAILABLE_TARGETS = ['UTF-8']
EXPECTED_C_LOCALE_EQUIVALENTS = ['C', 'invalid.ascii']
EXPECTED_C_LOCALE_STREAM_ENCODING = 'ascii'
EXPECTED_C_LOCALE_FS_ENCODING = 'utf-8'
EXPECT_COERCION_IN_DEFAULT_LOCALE = True
_C_UTF8_LOCALES = ('C.UTF-8', 'C.utf8', 'UTF-8')
_check_nl_langinfo_CODESET = False
test_LC_ALL_set_to_C (test.test_c_locale_coercion.LocaleCoercionTests.test_LC_ALL_set_to_C) ... 
  test_LC_ALL_set_to_C (test.test_c_locale_coercion.LocaleCoercionTests.test_LC_ALL_set_to_C) (default_locale=True, PYTHONCOERCECLOCALE=None) ... FAIL
  test_LC_ALL_set_to_C (test.test_c_locale_coercion.LocaleCoercionTests.test_LC_ALL_set_to_C) (env_var='LANG', nominal_locale='C', PYTHONCOERCECLOCALE=None) ... FAIL
  test_LC_ALL_set_to_C (test.test_c_locale_coercion.LocaleCoercionTests.test_LC_ALL_set_to_C) (env_var='LC_CTYPE', nominal_locale='C', PYTHONCOERCECLOCALE=None) ... FAIL
  test_LC_ALL_set_to_C (test.test_c_locale_coercion.LocaleCoercionTests.test_LC_ALL_set_to_C) (env_var='LANG', nominal_locale='invalid.ascii', PYTHONCOERCECLOCALE=None) ... FAIL
  test_LC_ALL_set_to_C (test.test_c_locale_coercion.LocaleCoercionTests.test_LC_ALL_set_to_C) (env_var='LC_CTYPE', nominal_locale='invalid.ascii', PYTHONCOERCECLOCALE=None) ... FAIL
  test_LC_ALL_set_to_C (test.test_c_locale_coercion.LocaleCoercionTests.test_LC_ALL_set_to_C) (default_locale=True, PYTHONCOERCECLOCALE='warn') ... FAIL
  test_LC_ALL_set_to_C (test.test_c_locale_coercion.LocaleCoercionTests.test_LC_ALL_set_to_C) (env_var='LANG', nominal_locale='C', PYTHONCOERCECLOCALE='warn') ... FAIL
  test_LC_ALL_set_to_C (test.test_c_locale_coercion.LocaleCoercionTests.test_LC_ALL_set_to_C) (env_var='LC_CTYPE', nominal_locale='C', PYTHONCOERCECLOCALE='warn') ... FAIL
  test_LC_ALL_set_to_C (test.test_c_locale_coercion.LocaleCoercionTests.test_LC_ALL_set_to_C) (env_var='LANG', nominal_locale='invalid.ascii', PYTHONCOERCECLOCALE='warn') ... FAIL
  test_LC_ALL_set_to_C (test.test_c_locale_coercion.LocaleCoercionTests.test_LC_ALL_set_to_C) (env_var='LC_CTYPE', nominal_locale='invalid.ascii', PYTHONCOERCECLOCALE='warn') ... FAIL
test_PYTHONCOERCECLOCALE_not_set (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_not_set) ... ok
test_PYTHONCOERCECLOCALE_not_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_not_zero) ... ok
test_PYTHONCOERCECLOCALE_set_to_one (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_one) ... skipped 'coerced LC_CTYPE locale: UTF-8'
test_PYTHONCOERCECLOCALE_set_to_warn (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_warn) ... ok
test_PYTHONCOERCECLOCALE_set_to_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_zero) ... 
  test_PYTHONCOERCECLOCALE_set_to_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_zero) (default_locale=True, PYTHONCOERCECLOCALE='0') ... FAIL
  test_PYTHONCOERCECLOCALE_set_to_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_zero) (env_var='LANG', nominal_locale='C', PYTHONCOERCECLOCALE='0') ... FAIL
  test_PYTHONCOERCECLOCALE_set_to_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_zero) (env_var='LC_CTYPE', nominal_locale='C', PYTHONCOERCECLOCALE='0') ... FAIL
  test_PYTHONCOERCECLOCALE_set_to_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_zero) (env_var='LANG', nominal_locale='invalid.ascii', PYTHONCOERCECLOCALE='0') ... FAIL
  test_PYTHONCOERCECLOCALE_set_to_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_zero) (env_var='LC_CTYPE', nominal_locale='invalid.ascii', PYTHONCOERCECLOCALE='0') ... FAIL
  test_PYTHONCOERCECLOCALE_set_to_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_zero) (default_locale=True, PYTHONCOERCECLOCALE='0') ... FAIL
  test_PYTHONCOERCECLOCALE_set_to_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_zero) (env_var='LANG', nominal_locale='C', PYTHONCOERCECLOCALE='0') ... FAIL
  test_PYTHONCOERCECLOCALE_set_to_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_zero) (env_var='LC_CTYPE', nominal_locale='C', PYTHONCOERCECLOCALE='0') ... FAIL
  test_PYTHONCOERCECLOCALE_set_to_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_zero) (env_var='LANG', nominal_locale='invalid.ascii', PYTHONCOERCECLOCALE='0') ... FAIL
  test_PYTHONCOERCECLOCALE_set_to_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_zero) (env_var='LC_CTYPE', nominal_locale='invalid.ascii', PYTHONCOERCECLOCALE='0') ... FAIL
test_external_target_locale_configuration (test.test_c_locale_coercion.LocaleConfigurationTests.test_external_target_locale_configuration) ... ok

======================================================================
FAIL: test_LC_ALL_set_to_C (test.test_c_locale_coercion.LocaleCoercionTests.test_LC_ALL_set_to_C) (default_locale=True, PYTHONCOERCECLOCALE=None)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 340, in _check_c_locale_coercion
    self._check_child_encoding_details(base_var_dict,
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^
                                       fs_encoding,
                                       ^^^^^^^^^^^^
                                       stream_encoding,
                                       ^^^^^^^^^^^^^^^^
                                       _expected_warnings,
                                       ^^^^^^^^^^^^^^^^^^^
                                       _coercion_expected)
                                       ^^^^^^^^^^^^^^^^^^^
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 230, in _check_child_encoding_details
    self.assertEqual(encoding_details, expected_details)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: {'fse[29 chars]o': 'utf-8:surrogateescape', 'stdout_info': 'u[101 chars] 'C'} != {'fse[29 chars]o': 'ascii:surrogateescape', 'stdout_info': 'a[101 chars] 'C'}
  {'fsencoding': 'utf-8',
   'lang': '',
   'lc_all': 'C',
   'lc_ctype': '',
-  'stderr_info': 'utf-8:backslashreplace',
?                  ^^^^^

+  'stderr_info': 'ascii:backslashreplace',
?                  ^^^^^

-  'stdin_info': 'utf-8:surrogateescape',
?                 ^^^^^

+  'stdin_info': 'ascii:surrogateescape',
?                 ^^^^^

-  'stdout_info': 'utf-8:surrogateescape'}
?                  ^^^^^

+  'stdout_info': 'ascii:surrogateescape'}
?                  ^^^^^


======================================================================
FAIL: test_LC_ALL_set_to_C (test.test_c_locale_coercion.LocaleCoercionTests.test_LC_ALL_set_to_C) (env_var='LANG', nominal_locale='C', PYTHONCOERCECLOCALE=None)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 355, in _check_c_locale_coercion
    self._check_child_encoding_details(var_dict,
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
                                       fs_encoding,
                                       ^^^^^^^^^^^^
                                       stream_encoding,
                                       ^^^^^^^^^^^^^^^^
                                       expected_warnings,
                                       ^^^^^^^^^^^^^^^^^^
                                       coercion_expected)
                                       ^^^^^^^^^^^^^^^^^^
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 230, in _check_child_encoding_details
    self.assertEqual(encoding_details, expected_details)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: {'fse[29 chars]o': 'utf-8:surrogateescape', 'stdout_info': 'u[102 chars] 'C'} != {'fse[29 chars]o': 'ascii:surrogateescape', 'stdout_info': 'a[102 chars] 'C'}
  {'fsencoding': 'utf-8',
   'lang': 'C',
   'lc_all': 'C',
   'lc_ctype': '',
-  'stderr_info': 'utf-8:backslashreplace',
?                  ^^^^^

+  'stderr_info': 'ascii:backslashreplace',
?                  ^^^^^

-  'stdin_info': 'utf-8:surrogateescape',
?                 ^^^^^

+  'stdin_info': 'ascii:surrogateescape',
?                 ^^^^^

-  'stdout_info': 'utf-8:surrogateescape'}
?                  ^^^^^

+  'stdout_info': 'ascii:surrogateescape'}
?                  ^^^^^


======================================================================
FAIL: test_LC_ALL_set_to_C (test.test_c_locale_coercion.LocaleCoercionTests.test_LC_ALL_set_to_C) (env_var='LC_CTYPE', nominal_locale='C', PYTHONCOERCECLOCALE=None)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 355, in _check_c_locale_coercion
    self._check_child_encoding_details(var_dict,
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
                                       fs_encoding,
                                       ^^^^^^^^^^^^
                                       stream_encoding,
                                       ^^^^^^^^^^^^^^^^
                                       expected_warnings,
                                       ^^^^^^^^^^^^^^^^^^
                                       coercion_expected)
                                       ^^^^^^^^^^^^^^^^^^
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 230, in _check_child_encoding_details
    self.assertEqual(encoding_details, expected_details)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: {'fse[29 chars]o': 'utf-8:surrogateescape', 'stdout_info': 'u[102 chars] 'C'} != {'fse[29 chars]o': 'ascii:surrogateescape', 'stdout_info': 'a[102 chars] 'C'}
  {'fsencoding': 'utf-8',
   'lang': '',
   'lc_all': 'C',
   'lc_ctype': 'C',
-  'stderr_info': 'utf-8:backslashreplace',
?                  ^^^^^

+  'stderr_info': 'ascii:backslashreplace',
?                  ^^^^^

-  'stdin_info': 'utf-8:surrogateescape',
?                 ^^^^^

+  'stdin_info': 'ascii:surrogateescape',
?                 ^^^^^

-  'stdout_info': 'utf-8:surrogateescape'}
?                  ^^^^^

+  'stdout_info': 'ascii:surrogateescape'}
?                  ^^^^^


======================================================================
FAIL: test_LC_ALL_set_to_C (test.test_c_locale_coercion.LocaleCoercionTests.test_LC_ALL_set_to_C) (env_var='LANG', nominal_locale='invalid.ascii', PYTHONCOERCECLOCALE=None)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 355, in _check_c_locale_coercion
    self._check_child_encoding_details(var_dict,
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
                                       fs_encoding,
                                       ^^^^^^^^^^^^
                                       stream_encoding,
                                       ^^^^^^^^^^^^^^^^
                                       expected_warnings,
                                       ^^^^^^^^^^^^^^^^^^
                                       coercion_expected)
                                       ^^^^^^^^^^^^^^^^^^
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 230, in _check_child_encoding_details
    self.assertEqual(encoding_details, expected_details)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: {'fse[29 chars]o': 'utf-8:surrogateescape', 'stdout_info': 'u[114 chars] 'C'} != {'fse[29 chars]o': 'ascii:surrogateescape', 'stdout_info': 'a[114 chars] 'C'}
  {'fsencoding': 'utf-8',
   'lang': 'invalid.ascii',
   'lc_all': 'C',
   'lc_ctype': '',
-  'stderr_info': 'utf-8:backslashreplace',
?                  ^^^^^

+  'stderr_info': 'ascii:backslashreplace',
?                  ^^^^^

-  'stdin_info': 'utf-8:surrogateescape',
?                 ^^^^^

+  'stdin_info': 'ascii:surrogateescape',
?                 ^^^^^

-  'stdout_info': 'utf-8:surrogateescape'}
?                  ^^^^^

+  'stdout_info': 'ascii:surrogateescape'}
?                  ^^^^^


======================================================================
FAIL: test_LC_ALL_set_to_C (test.test_c_locale_coercion.LocaleCoercionTests.test_LC_ALL_set_to_C) (env_var='LC_CTYPE', nominal_locale='invalid.ascii', PYTHONCOERCECLOCALE=None)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 355, in _check_c_locale_coercion
    self._check_child_encoding_details(var_dict,
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
                                       fs_encoding,
                                       ^^^^^^^^^^^^
                                       stream_encoding,
                                       ^^^^^^^^^^^^^^^^
                                       expected_warnings,
                                       ^^^^^^^^^^^^^^^^^^
                                       coercion_expected)
                                       ^^^^^^^^^^^^^^^^^^
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 230, in _check_child_encoding_details
    self.assertEqual(encoding_details, expected_details)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: {'fse[29 chars]o': 'utf-8:surrogateescape', 'stdout_info': 'u[114 chars] 'C'} != {'fse[29 chars]o': 'ascii:surrogateescape', 'stdout_info': 'a[114 chars] 'C'}
  {'fsencoding': 'utf-8',
   'lang': '',
   'lc_all': 'C',
   'lc_ctype': 'invalid.ascii',
-  'stderr_info': 'utf-8:backslashreplace',
?                  ^^^^^

+  'stderr_info': 'ascii:backslashreplace',
?                  ^^^^^

-  'stdin_info': 'utf-8:surrogateescape',
?                 ^^^^^

+  'stdin_info': 'ascii:surrogateescape',
?                 ^^^^^

-  'stdout_info': 'utf-8:surrogateescape'}
?                  ^^^^^

+  'stdout_info': 'ascii:surrogateescape'}
?                  ^^^^^


======================================================================
FAIL: test_LC_ALL_set_to_C (test.test_c_locale_coercion.LocaleCoercionTests.test_LC_ALL_set_to_C) (default_locale=True, PYTHONCOERCECLOCALE='warn')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 340, in _check_c_locale_coercion
    self._check_child_encoding_details(base_var_dict,
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^
                                       fs_encoding,
                                       ^^^^^^^^^^^^
                                       stream_encoding,
                                       ^^^^^^^^^^^^^^^^
                                       _expected_warnings,
                                       ^^^^^^^^^^^^^^^^^^^
                                       _coercion_expected)
                                       ^^^^^^^^^^^^^^^^^^^
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 230, in _check_child_encoding_details
    self.assertEqual(encoding_details, expected_details)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: {'fse[29 chars]o': 'utf-8:surrogateescape', 'stdout_info': 'u[101 chars] 'C'} != {'fse[29 chars]o': 'ascii:surrogateescape', 'stdout_info': 'a[101 chars] 'C'}
  {'fsencoding': 'utf-8',
   'lang': '',
   'lc_all': 'C',
   'lc_ctype': '',
-  'stderr_info': 'utf-8:backslashreplace',
?                  ^^^^^

+  'stderr_info': 'ascii:backslashreplace',
?                  ^^^^^

-  'stdin_info': 'utf-8:surrogateescape',
?                 ^^^^^

+  'stdin_info': 'ascii:surrogateescape',
?                 ^^^^^

-  'stdout_info': 'utf-8:surrogateescape'}
?                  ^^^^^

+  'stdout_info': 'ascii:surrogateescape'}
?                  ^^^^^


======================================================================
FAIL: test_LC_ALL_set_to_C (test.test_c_locale_coercion.LocaleCoercionTests.test_LC_ALL_set_to_C) (env_var='LANG', nominal_locale='C', PYTHONCOERCECLOCALE='warn')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 355, in _check_c_locale_coercion
    self._check_child_encoding_details(var_dict,
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
                                       fs_encoding,
                                       ^^^^^^^^^^^^
                                       stream_encoding,
                                       ^^^^^^^^^^^^^^^^
                                       expected_warnings,
                                       ^^^^^^^^^^^^^^^^^^
                                       coercion_expected)
                                       ^^^^^^^^^^^^^^^^^^
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 230, in _check_child_encoding_details
    self.assertEqual(encoding_details, expected_details)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: {'fse[29 chars]o': 'utf-8:surrogateescape', 'stdout_info': 'u[102 chars] 'C'} != {'fse[29 chars]o': 'ascii:surrogateescape', 'stdout_info': 'a[102 chars] 'C'}
  {'fsencoding': 'utf-8',
   'lang': 'C',
   'lc_all': 'C',
   'lc_ctype': '',
-  'stderr_info': 'utf-8:backslashreplace',
?                  ^^^^^

+  'stderr_info': 'ascii:backslashreplace',
?                  ^^^^^

-  'stdin_info': 'utf-8:surrogateescape',
?                 ^^^^^

+  'stdin_info': 'ascii:surrogateescape',
?                 ^^^^^

-  'stdout_info': 'utf-8:surrogateescape'}
?                  ^^^^^

+  'stdout_info': 'ascii:surrogateescape'}
?                  ^^^^^


======================================================================
FAIL: test_LC_ALL_set_to_C (test.test_c_locale_coercion.LocaleCoercionTests.test_LC_ALL_set_to_C) (env_var='LC_CTYPE', nominal_locale='C', PYTHONCOERCECLOCALE='warn')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 355, in _check_c_locale_coercion
    self._check_child_encoding_details(var_dict,
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
                                       fs_encoding,
                                       ^^^^^^^^^^^^
                                       stream_encoding,
                                       ^^^^^^^^^^^^^^^^
                                       expected_warnings,
                                       ^^^^^^^^^^^^^^^^^^
                                       coercion_expected)
                                       ^^^^^^^^^^^^^^^^^^
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 230, in _check_child_encoding_details
    self.assertEqual(encoding_details, expected_details)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: {'fse[29 chars]o': 'utf-8:surrogateescape', 'stdout_info': 'u[102 chars] 'C'} != {'fse[29 chars]o': 'ascii:surrogateescape', 'stdout_info': 'a[102 chars] 'C'}
  {'fsencoding': 'utf-8',
   'lang': '',
   'lc_all': 'C',
   'lc_ctype': 'C',
-  'stderr_info': 'utf-8:backslashreplace',
?                  ^^^^^

+  'stderr_info': 'ascii:backslashreplace',
?                  ^^^^^

-  'stdin_info': 'utf-8:surrogateescape',
?                 ^^^^^

+  'stdin_info': 'ascii:surrogateescape',
?                 ^^^^^

-  'stdout_info': 'utf-8:surrogateescape'}
?                  ^^^^^

+  'stdout_info': 'ascii:surrogateescape'}
?                  ^^^^^


======================================================================
FAIL: test_LC_ALL_set_to_C (test.test_c_locale_coercion.LocaleCoercionTests.test_LC_ALL_set_to_C) (env_var='LANG', nominal_locale='invalid.ascii', PYTHONCOERCECLOCALE='warn')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 355, in _check_c_locale_coercion
    self._check_child_encoding_details(var_dict,
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
                                       fs_encoding,
                                       ^^^^^^^^^^^^
                                       stream_encoding,
                                       ^^^^^^^^^^^^^^^^
                                       expected_warnings,
                                       ^^^^^^^^^^^^^^^^^^
                                       coercion_expected)
                                       ^^^^^^^^^^^^^^^^^^
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 230, in _check_child_encoding_details
    self.assertEqual(encoding_details, expected_details)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: {'fse[29 chars]o': 'utf-8:surrogateescape', 'stdout_info': 'u[114 chars] 'C'} != {'fse[29 chars]o': 'ascii:surrogateescape', 'stdout_info': 'a[114 chars] 'C'}
  {'fsencoding': 'utf-8',
   'lang': 'invalid.ascii',
   'lc_all': 'C',
   'lc_ctype': '',
-  'stderr_info': 'utf-8:backslashreplace',
?                  ^^^^^

+  'stderr_info': 'ascii:backslashreplace',
?                  ^^^^^

-  'stdin_info': 'utf-8:surrogateescape',
?                 ^^^^^

+  'stdin_info': 'ascii:surrogateescape',
?                 ^^^^^

-  'stdout_info': 'utf-8:surrogateescape'}
?                  ^^^^^

+  'stdout_info': 'ascii:surrogateescape'}
?                  ^^^^^


======================================================================
FAIL: test_LC_ALL_set_to_C (test.test_c_locale_coercion.LocaleCoercionTests.test_LC_ALL_set_to_C) (env_var='LC_CTYPE', nominal_locale='invalid.ascii', PYTHONCOERCECLOCALE='warn')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 355, in _check_c_locale_coercion
    self._check_child_encoding_details(var_dict,
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
                                       fs_encoding,
                                       ^^^^^^^^^^^^
                                       stream_encoding,
                                       ^^^^^^^^^^^^^^^^
                                       expected_warnings,
                                       ^^^^^^^^^^^^^^^^^^
                                       coercion_expected)
                                       ^^^^^^^^^^^^^^^^^^
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 230, in _check_child_encoding_details
    self.assertEqual(encoding_details, expected_details)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: {'fse[29 chars]o': 'utf-8:surrogateescape', 'stdout_info': 'u[114 chars] 'C'} != {'fse[29 chars]o': 'ascii:surrogateescape', 'stdout_info': 'a[114 chars] 'C'}
  {'fsencoding': 'utf-8',
   'lang': '',
   'lc_all': 'C',
   'lc_ctype': 'invalid.ascii',
-  'stderr_info': 'utf-8:backslashreplace',
?                  ^^^^^

+  'stderr_info': 'ascii:backslashreplace',
?                  ^^^^^

-  'stdin_info': 'utf-8:surrogateescape',
?                 ^^^^^

+  'stdin_info': 'ascii:surrogateescape',
?                 ^^^^^

-  'stdout_info': 'utf-8:surrogateescape'}
?                  ^^^^^

+  'stdout_info': 'ascii:surrogateescape'}
?                  ^^^^^


======================================================================
FAIL: test_PYTHONCOERCECLOCALE_set_to_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_zero) (default_locale=True, PYTHONCOERCECLOCALE='0')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 340, in _check_c_locale_coercion
    self._check_child_encoding_details(base_var_dict,
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^
                                       fs_encoding,
                                       ^^^^^^^^^^^^
                                       stream_encoding,
                                       ^^^^^^^^^^^^^^^^
                                       _expected_warnings,
                                       ^^^^^^^^^^^^^^^^^^^
                                       _coercion_expected)
                                       ^^^^^^^^^^^^^^^^^^^
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 230, in _check_child_encoding_details
    self.assertEqual(encoding_details, expected_details)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: {'fse[29 chars]o': 'utf-8:surrogateescape', 'stdout_info': 'u[100 chars]: ''} != {'fse[29 chars]o': 'ascii:surrogateescape', 'stdout_info': 'a[100 chars]: ''}
  {'fsencoding': 'utf-8',
   'lang': '',
   'lc_all': '',
   'lc_ctype': '',
-  'stderr_info': 'utf-8:backslashreplace',
?                  ^^^^^

+  'stderr_info': 'ascii:backslashreplace',
?                  ^^^^^

-  'stdin_info': 'utf-8:surrogateescape',
?                 ^^^^^

+  'stdin_info': 'ascii:surrogateescape',
?                 ^^^^^

-  'stdout_info': 'utf-8:surrogateescape'}
?                  ^^^^^

+  'stdout_info': 'ascii:surrogateescape'}
?                  ^^^^^


======================================================================
FAIL: test_PYTHONCOERCECLOCALE_set_to_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_zero) (env_var='LANG', nominal_locale='C', PYTHONCOERCECLOCALE='0')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 355, in _check_c_locale_coercion
    self._check_child_encoding_details(var_dict,
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
                                       fs_encoding,
                                       ^^^^^^^^^^^^
                                       stream_encoding,
                                       ^^^^^^^^^^^^^^^^
                                       expected_warnings,
                                       ^^^^^^^^^^^^^^^^^^
                                       coercion_expected)
                                       ^^^^^^^^^^^^^^^^^^
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 230, in _check_child_encoding_details
    self.assertEqual(encoding_details, expected_details)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: {'fse[29 chars]o': 'utf-8:surrogateescape', 'stdout_info': 'u[101 chars]: ''} != {'fse[29 chars]o': 'ascii:surrogateescape', 'stdout_info': 'a[101 chars]: ''}
  {'fsencoding': 'utf-8',
   'lang': 'C',
   'lc_all': '',
   'lc_ctype': '',
-  'stderr_info': 'utf-8:backslashreplace',
?                  ^^^^^

+  'stderr_info': 'ascii:backslashreplace',
?                  ^^^^^

-  'stdin_info': 'utf-8:surrogateescape',
?                 ^^^^^

+  'stdin_info': 'ascii:surrogateescape',
?                 ^^^^^

-  'stdout_info': 'utf-8:surrogateescape'}
?                  ^^^^^

+  'stdout_info': 'ascii:surrogateescape'}
?                  ^^^^^


======================================================================
FAIL: test_PYTHONCOERCECLOCALE_set_to_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_zero) (env_var='LC_CTYPE', nominal_locale='C', PYTHONCOERCECLOCALE='0')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 355, in _check_c_locale_coercion
    self._check_child_encoding_details(var_dict,
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
                                       fs_encoding,
                                       ^^^^^^^^^^^^
                                       stream_encoding,
                                       ^^^^^^^^^^^^^^^^
                                       expected_warnings,
                                       ^^^^^^^^^^^^^^^^^^
                                       coercion_expected)
                                       ^^^^^^^^^^^^^^^^^^
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 230, in _check_child_encoding_details
    self.assertEqual(encoding_details, expected_details)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: {'fse[29 chars]o': 'utf-8:surrogateescape', 'stdout_info': 'u[101 chars]: ''} != {'fse[29 chars]o': 'ascii:surrogateescape', 'stdout_info': 'a[101 chars]: ''}
  {'fsencoding': 'utf-8',
   'lang': '',
   'lc_all': '',
   'lc_ctype': 'C',
-  'stderr_info': 'utf-8:backslashreplace',
?                  ^^^^^

+  'stderr_info': 'ascii:backslashreplace',
?                  ^^^^^

-  'stdin_info': 'utf-8:surrogateescape',
?                 ^^^^^

+  'stdin_info': 'ascii:surrogateescape',
?                 ^^^^^

-  'stdout_info': 'utf-8:surrogateescape'}
?                  ^^^^^

+  'stdout_info': 'ascii:surrogateescape'}
?                  ^^^^^


======================================================================
FAIL: test_PYTHONCOERCECLOCALE_set_to_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_zero) (env_var='LANG', nominal_locale='invalid.ascii', PYTHONCOERCECLOCALE='0')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 355, in _check_c_locale_coercion
    self._check_child_encoding_details(var_dict,
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
                                       fs_encoding,
                                       ^^^^^^^^^^^^
                                       stream_encoding,
                                       ^^^^^^^^^^^^^^^^
                                       expected_warnings,
                                       ^^^^^^^^^^^^^^^^^^
                                       coercion_expected)
                                       ^^^^^^^^^^^^^^^^^^
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 230, in _check_child_encoding_details
    self.assertEqual(encoding_details, expected_details)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: {'fse[29 chars]o': 'utf-8:surrogateescape', 'stdout_info': 'u[113 chars]: ''} != {'fse[29 chars]o': 'ascii:surrogateescape', 'stdout_info': 'a[113 chars]: ''}
  {'fsencoding': 'utf-8',
   'lang': 'invalid.ascii',
   'lc_all': '',
   'lc_ctype': '',
-  'stderr_info': 'utf-8:backslashreplace',
?                  ^^^^^

+  'stderr_info': 'ascii:backslashreplace',
?                  ^^^^^

-  'stdin_info': 'utf-8:surrogateescape',
?                 ^^^^^

+  'stdin_info': 'ascii:surrogateescape',
?                 ^^^^^

-  'stdout_info': 'utf-8:surrogateescape'}
?                  ^^^^^

+  'stdout_info': 'ascii:surrogateescape'}
?                  ^^^^^


======================================================================
FAIL: test_PYTHONCOERCECLOCALE_set_to_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_zero) (env_var='LC_CTYPE', nominal_locale='invalid.ascii', PYTHONCOERCECLOCALE='0')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 355, in _check_c_locale_coercion
    self._check_child_encoding_details(var_dict,
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
                                       fs_encoding,
                                       ^^^^^^^^^^^^
                                       stream_encoding,
                                       ^^^^^^^^^^^^^^^^
                                       expected_warnings,
                                       ^^^^^^^^^^^^^^^^^^
                                       coercion_expected)
                                       ^^^^^^^^^^^^^^^^^^
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 230, in _check_child_encoding_details
    self.assertEqual(encoding_details, expected_details)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: {'fse[29 chars]o': 'utf-8:surrogateescape', 'stdout_info': 'u[113 chars]: ''} != {'fse[29 chars]o': 'ascii:surrogateescape', 'stdout_info': 'a[113 chars]: ''}
  {'fsencoding': 'utf-8',
   'lang': '',
   'lc_all': '',
   'lc_ctype': 'invalid.ascii',
-  'stderr_info': 'utf-8:backslashreplace',
?                  ^^^^^

+  'stderr_info': 'ascii:backslashreplace',
?                  ^^^^^

-  'stdin_info': 'utf-8:surrogateescape',
?                 ^^^^^

+  'stdin_info': 'ascii:surrogateescape',
?                 ^^^^^

-  'stdout_info': 'utf-8:surrogateescape'}
?                  ^^^^^

+  'stdout_info': 'ascii:surrogateescape'}
?                  ^^^^^


======================================================================
FAIL: test_PYTHONCOERCECLOCALE_set_to_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_zero) (default_locale=True, PYTHONCOERCECLOCALE='0')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 340, in _check_c_locale_coercion
    self._check_child_encoding_details(base_var_dict,
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^
                                       fs_encoding,
                                       ^^^^^^^^^^^^
                                       stream_encoding,
                                       ^^^^^^^^^^^^^^^^
                                       _expected_warnings,
                                       ^^^^^^^^^^^^^^^^^^^
                                       _coercion_expected)
                                       ^^^^^^^^^^^^^^^^^^^
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 230, in _check_child_encoding_details
    self.assertEqual(encoding_details, expected_details)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: {'fse[29 chars]o': 'utf-8:surrogateescape', 'stdout_info': 'u[101 chars] 'C'} != {'fse[29 chars]o': 'ascii:surrogateescape', 'stdout_info': 'a[101 chars] 'C'}
  {'fsencoding': 'utf-8',
   'lang': '',
   'lc_all': 'C',
   'lc_ctype': '',
-  'stderr_info': 'utf-8:backslashreplace',
?                  ^^^^^

+  'stderr_info': 'ascii:backslashreplace',
?                  ^^^^^

-  'stdin_info': 'utf-8:surrogateescape',
?                 ^^^^^

+  'stdin_info': 'ascii:surrogateescape',
?                 ^^^^^

-  'stdout_info': 'utf-8:surrogateescape'}
?                  ^^^^^

+  'stdout_info': 'ascii:surrogateescape'}
?                  ^^^^^


======================================================================
FAIL: test_PYTHONCOERCECLOCALE_set_to_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_zero) (env_var='LANG', nominal_locale='C', PYTHONCOERCECLOCALE='0')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 355, in _check_c_locale_coercion
    self._check_child_encoding_details(var_dict,
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
                                       fs_encoding,
                                       ^^^^^^^^^^^^
                                       stream_encoding,
                                       ^^^^^^^^^^^^^^^^
                                       expected_warnings,
                                       ^^^^^^^^^^^^^^^^^^
                                       coercion_expected)
                                       ^^^^^^^^^^^^^^^^^^
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 230, in _check_child_encoding_details
    self.assertEqual(encoding_details, expected_details)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: {'fse[29 chars]o': 'utf-8:surrogateescape', 'stdout_info': 'u[102 chars] 'C'} != {'fse[29 chars]o': 'ascii:surrogateescape', 'stdout_info': 'a[102 chars] 'C'}
  {'fsencoding': 'utf-8',
   'lang': 'C',
   'lc_all': 'C',
   'lc_ctype': '',
-  'stderr_info': 'utf-8:backslashreplace',
?                  ^^^^^

+  'stderr_info': 'ascii:backslashreplace',
?                  ^^^^^

-  'stdin_info': 'utf-8:surrogateescape',
?                 ^^^^^

+  'stdin_info': 'ascii:surrogateescape',
?                 ^^^^^

-  'stdout_info': 'utf-8:surrogateescape'}
?                  ^^^^^

+  'stdout_info': 'ascii:surrogateescape'}
?                  ^^^^^


======================================================================
FAIL: test_PYTHONCOERCECLOCALE_set_to_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_zero) (env_var='LC_CTYPE', nominal_locale='C', PYTHONCOERCECLOCALE='0')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 355, in _check_c_locale_coercion
    self._check_child_encoding_details(var_dict,
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
                                       fs_encoding,
                                       ^^^^^^^^^^^^
                                       stream_encoding,
                                       ^^^^^^^^^^^^^^^^
                                       expected_warnings,
                                       ^^^^^^^^^^^^^^^^^^
                                       coercion_expected)
                                       ^^^^^^^^^^^^^^^^^^
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 230, in _check_child_encoding_details
    self.assertEqual(encoding_details, expected_details)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: {'fse[29 chars]o': 'utf-8:surrogateescape', 'stdout_info': 'u[102 chars] 'C'} != {'fse[29 chars]o': 'ascii:surrogateescape', 'stdout_info': 'a[102 chars] 'C'}
  {'fsencoding': 'utf-8',
   'lang': '',
   'lc_all': 'C',
   'lc_ctype': 'C',
-  'stderr_info': 'utf-8:backslashreplace',
?                  ^^^^^

+  'stderr_info': 'ascii:backslashreplace',
?                  ^^^^^

-  'stdin_info': 'utf-8:surrogateescape',
?                 ^^^^^

+  'stdin_info': 'ascii:surrogateescape',
?                 ^^^^^

-  'stdout_info': 'utf-8:surrogateescape'}
?                  ^^^^^

+  'stdout_info': 'ascii:surrogateescape'}
?                  ^^^^^


======================================================================
FAIL: test_PYTHONCOERCECLOCALE_set_to_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_zero) (env_var='LANG', nominal_locale='invalid.ascii', PYTHONCOERCECLOCALE='0')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 355, in _check_c_locale_coercion
    self._check_child_encoding_details(var_dict,
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
                                       fs_encoding,
                                       ^^^^^^^^^^^^
                                       stream_encoding,
                                       ^^^^^^^^^^^^^^^^
                                       expected_warnings,
                                       ^^^^^^^^^^^^^^^^^^
                                       coercion_expected)
                                       ^^^^^^^^^^^^^^^^^^
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 230, in _check_child_encoding_details
    self.assertEqual(encoding_details, expected_details)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: {'fse[29 chars]o': 'utf-8:surrogateescape', 'stdout_info': 'u[114 chars] 'C'} != {'fse[29 chars]o': 'ascii:surrogateescape', 'stdout_info': 'a[114 chars] 'C'}
  {'fsencoding': 'utf-8',
   'lang': 'invalid.ascii',
   'lc_all': 'C',
   'lc_ctype': '',
-  'stderr_info': 'utf-8:backslashreplace',
?                  ^^^^^

+  'stderr_info': 'ascii:backslashreplace',
?                  ^^^^^

-  'stdin_info': 'utf-8:surrogateescape',
?                 ^^^^^

+  'stdin_info': 'ascii:surrogateescape',
?                 ^^^^^

-  'stdout_info': 'utf-8:surrogateescape'}
?                  ^^^^^

+  'stdout_info': 'ascii:surrogateescape'}
?                  ^^^^^


======================================================================
FAIL: test_PYTHONCOERCECLOCALE_set_to_zero (test.test_c_locale_coercion.LocaleCoercionTests.test_PYTHONCOERCECLOCALE_set_to_zero) (env_var='LC_CTYPE', nominal_locale='invalid.ascii', PYTHONCOERCECLOCALE='0')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 355, in _check_c_locale_coercion
    self._check_child_encoding_details(var_dict,
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
                                       fs_encoding,
                                       ^^^^^^^^^^^^
                                       stream_encoding,
                                       ^^^^^^^^^^^^^^^^
                                       expected_warnings,
                                       ^^^^^^^^^^^^^^^^^^
                                       coercion_expected)
                                       ^^^^^^^^^^^^^^^^^^
  File "/Users/ronald/Projects/Forks/cpython-upstream/Lib/test/test_c_locale_coercion.py", line 230, in _check_child_encoding_details
    self.assertEqual(encoding_details, expected_details)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: {'fse[29 chars]o': 'utf-8:surrogateescape', 'stdout_info': 'u[114 chars] 'C'} != {'fse[29 chars]o': 'ascii:surrogateescape', 'stdout_info': 'a[114 chars] 'C'}
  {'fsencoding': 'utf-8',
   'lang': '',
   'lc_all': 'C',
   'lc_ctype': 'invalid.ascii',
-  'stderr_info': 'utf-8:backslashreplace',
?                  ^^^^^

+  'stderr_info': 'ascii:backslashreplace',
?                  ^^^^^

-  'stdin_info': 'utf-8:surrogateescape',
?                 ^^^^^

+  'stdin_info': 'ascii:surrogateescape',
?                 ^^^^^

-  'stdout_info': 'utf-8:surrogateescape'}
?                  ^^^^^

+  'stdout_info': 'ascii:surrogateescape'}
?                  ^^^^^


----------------------------------------------------------------------
Ran 7 tests in 0.914s

FAILED (failures=20, skipped=1)
test test_c_locale_coercion failed
test_c_locale_coercion failed (20 failures)

== Tests result: FAILURE ==

1 test failed:
    test_c_locale_coercion

Total duration: 951 ms
Total tests: run=7 failures=20 skipped=1
Total test files: run=1/1 failed=1
Result: FAILURE

[sobolevn]

It still fails for me:

» env | grep PYTHONIOENCODING
PYTHONIOENCODING=UTF-8

» ./python.exe -m test test_c_locale_coercion   
Using random seed: 4256789499
0:00:00 load avg: 3.07 Run 1 test sequentially
0:00:00 load avg: 3.07 [1/1] test_c_locale_coercion
test test_c_locale_coercion failed -- multiple errors occurred; run in verbose mode for details
test_c_locale_coercion failed (51 failures)

== Tests result: FAILURE ==

1 test failed:
    test_c_locale_coercion

Total duration: 903 ms
Total tests: run=7 failures=51
Total test files: run=1/1 failed=1
Result: FAILURE

Looks like PYTHONIOENCODING is indeed related:

» unset PYTHONIOENCODING
                                                                                                                                              
» ./python.exe -m test test_c_locale_coercion
Using random seed: 554831913
0:00:00 load avg: 2.19 Run 1 test sequentially
0:00:00 load avg: 2.19 [1/1] test_c_locale_coercion

== Tests result: SUCCESS ==

1 test OK.

Total duration: 843 ms
Total tests: run=7
Total test files: run=1/1
Result: SUCCESS

[ronaldoussoren]

I can reproduce this with setting PYTHONIOENCODING to UTF-8.

This patch "fixes" the test failures, but I'm far from convinced that this is the right fix. There would at the very least need to be new tests that very the behaviour when PYTHONIOENCODING is set.

diff --git a/Lib/test/test_c_locale_coercion.py b/Lib/test/test_c_locale_coercion.py
index 71f934756e..bd103a00e8 100644
--- a/Lib/test/test_c_locale_coercion.py
+++ b/Lib/test/test_c_locale_coercion.py
@@ -257,6 +257,7 @@ def test_external_target_locale_configuration(self):
             "LC_CTYPE": "",
             "LC_ALL": "",
             "PYTHONCOERCECLOCALE": "",
+            "PYTHONIOENCODING": "",
         }
         for env_var in ("LANG", "LC_CTYPE"):
             for locale_to_set in AVAILABLE_TARGETS:
@@ -316,6 +317,7 @@ def _check_c_locale_coercion(self,
             "LC_CTYPE": "",
             "LC_ALL": "",
             "PYTHONCOERCECLOCALE": "",
+            "PYTHONIOENCODING": "",
         }
         base_var_dict.update(extra_vars)
         if coerce_c_locale is not None:
@@ -348,7 +350,8 @@ def _check_c_locale_coercion(self,
             for env_var in ("LANG", "LC_CTYPE"):
                 with self.subTest(env_var=env_var,
                                   nominal_locale=locale_to_set,
-                                  PYTHONCOERCECLOCALE=coerce_c_locale):
+                                  PYTHONCOERCECLOCALE=coerce_c_locale,
+                                  PYTHONIOENCODING=""):
                     var_dict = base_var_dict.copy()
                     var_dict[env_var] = locale_to_set
                     # Check behaviour on successful coercion

[ronaldoussoren]

Some more research:

• PYTHONCOERCECLOCALE is handled in Python/preconfig.c
• PYTHONIOENCODING is handled in Python/initconfig.c, in particular in config_init_stdio_encoding (see below)

cpython/Python/initconfig.c

Lines 1978 to 2059 in 8cdfee1

	static PyStatus
	config_init_stdio_encoding(PyConfig *config,
	const PyPreConfig *preconfig)
	{
	PyStatus status;
	// Exit if encoding and errors are defined
	if (config->stdio_encoding != NULL && config->stdio_errors != NULL) {
	return _PyStatus_OK();
	}
	/* PYTHONIOENCODING environment variable */
	const char *opt = config_get_env(config, "PYTHONIOENCODING");
	if (opt) {
	char *pythonioencoding = _PyMem_RawStrdup(opt);
	if (pythonioencoding == NULL) {
	return _PyStatus_NO_MEMORY();
	}
	char *errors = strchr(pythonioencoding, ':');
	if (errors) {
	*errors = '\0';
	errors++;
	if (!errors[0]) {
	errors = NULL;
	}
	}
	/* Does PYTHONIOENCODING contain an encoding? */
	if (pythonioencoding[0]) {
	if (config->stdio_encoding == NULL) {
	status = CONFIG_SET_BYTES_STR(config, &config->stdio_encoding,
	pythonioencoding,
	"PYTHONIOENCODING environment variable");
	if (_PyStatus_EXCEPTION(status)) {
	PyMem_RawFree(pythonioencoding);
	return status;
	}
	}
	/* If the encoding is set but not the error handler,
	use "strict" error handler by default.
	PYTHONIOENCODING=latin1 behaves as
	PYTHONIOENCODING=latin1:strict. */
	if (!errors) {
	errors = "strict";
	}
	}
	if (config->stdio_errors == NULL && errors != NULL) {
	status = CONFIG_SET_BYTES_STR(config, &config->stdio_errors,
	errors,
	"PYTHONIOENCODING environment variable");
	if (_PyStatus_EXCEPTION(status)) {
	PyMem_RawFree(pythonioencoding);
	return status;
	}
	}
	PyMem_RawFree(pythonioencoding);
	}
	/* Choose the default error handler based on the current locale. */
	if (config->stdio_encoding == NULL) {
	status = config_get_locale_encoding(config, preconfig,
	&config->stdio_encoding);
	if (_PyStatus_EXCEPTION(status)) {
	return status;
	}
	}
	if (config->stdio_errors == NULL) {
	const wchar_t *errors = config_get_stdio_errors(preconfig);
	assert(errors != NULL);
	status = PyConfig_SetString(config, &config->stdio_errors, errors);
	if (_PyStatus_EXCEPTION(status)) {
	return status;
	}
	}
	return _PyStatus_OK();
	}

PEP 538 introduced PYTHONCOERCECLOCALE and does not mention how the two settings should interact. That said, the current behaviour is present in at least 3.9 (the earliest version I can easily test) and should IMHO be considered as correct as changing will likely cause breakage.

Looks like my patch that suppressed the test failure by unsetting PYTHONIOENCODING is the best way to fix this after all, although ideally with a new test that checks behaviour when using both variables.

@ncoghlan and @methane, what's your opinion on the correct fix for this issue?