$ LC_ALL=uk_UA.koi8u ./python -m test
Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "/home/serhiy/py/cpython/Lib/test/__main__.py", line 2, in <module>
    main()
    ^^^^^^
  File "/home/serhiy/py/cpython/Lib/test/libregrtest/main.py", line 737, in main
    Regrtest().main(tests=tests, **kwargs)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/serhiy/py/cpython/Lib/contextlib.py", line 155, in __exit__
    self.gen.throw(typ, value, traceback)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/serhiy/py/cpython/Lib/contextlib.py", line 155, in __exit__
    self.gen.throw(typ, value, traceback)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/serhiy/py/cpython/Lib/test/support/os_helper.py", line 396, in temp_dir
    yield path
    ^^^^^^^^^^
  File "/home/serhiy/py/cpython/Lib/contextlib.py", line 155, in __exit__
    self.gen.throw(typ, value, traceback)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/serhiy/py/cpython/Lib/test/support/os_helper.py", line 427, in change_cwd
    yield os.getcwd()
    ^^^^^^^^^^^^^^^^^
  File "/home/serhiy/py/cpython/Lib/test/support/os_helper.py", line 449, in temp_cwd
    yield cwd_dir
    ^^^^^^^^^^^^^
  File "/home/serhiy/py/cpython/Lib/test/libregrtest/main.py", line 675, in main
    self._main(tests, kwargs)
    ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/serhiy/py/cpython/Lib/test/libregrtest/main.py", line 704, in _main
    setup_tests(self.ns)
    ^^^^^^^^^^^^^^^^^^^^
  File "/home/serhiy/py/cpython/Lib/test/libregrtest/setup.py", line 107, in setup_tests
    os.environ.setdefault(
    ^^^^^^^^^^^^^^^^^^^^^^
  File "<frozen os>", line 717, in setdefault
  File "<frozen os>", line 683, in __setitem__
  File "<frozen os>", line 758, in encode
  File "/home/serhiy/py/cpython/Lib/encodings/koi8_u.py", line 12, in encode
    return codecs.charmap_encode(input,errors,encoding_table)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
UnicodeEncodeError: 'charmap' codec can't encode character '\U0001f60e' in position 0: character maps to <undefined>