ResourceWarning in test.test_ucn.UnicodeNamesTest.test_named_sequences_full (when http request 404s)

[graingert]

Bug report

Bug description:

$ PYTHONTRACEMALLOC=25 ./python -Walways -m unittest test.test_ucn -vvv
test_aliases (test.test_ucn.UnicodeNamesTest.test_aliases) ... ok
test_aliases_names_in_pua_range (test.test_ucn.UnicodeNamesTest.test_aliases_names_in_pua_range) ... ok
test_ascii_letters (test.test_ucn.UnicodeNamesTest.test_ascii_letters) ... ok
test_bmp_characters (test.test_ucn.UnicodeNamesTest.test_bmp_characters) ... ok
test_cjk_unified_ideographs (test.test_ucn.UnicodeNamesTest.test_cjk_unified_ideographs) ... ok
test_errors (test.test_ucn.UnicodeNamesTest.test_errors) ... ok
test_general (test.test_ucn.UnicodeNamesTest.test_general) ... ok
test_hangul_syllables (test.test_ucn.UnicodeNamesTest.test_hangul_syllables) ... ok
test_issue16335 (test.test_ucn.UnicodeNamesTest.test_issue16335) ... skipped 'not enough memory: 12.0G minimum needed'
test_misc_symbols (test.test_ucn.UnicodeNamesTest.test_misc_symbols) ... ok
test_named_sequences_full (test.test_ucn.UnicodeNamesTest.test_named_sequences_full) ... 	fetching http://www.pythontest.net/unicode/15.1.0/NamedSequences.txt ...
skipped "Could not retrieve http://www.pythontest.net/unicode/15.1.0/NamedSequences.txt e=<HTTPError 404: 'Not Found'>"
test_named_sequences_names_in_pua_range (test.test_ucn.UnicodeNamesTest.test_named_sequences_names_in_pua_range) ... ok
test_named_sequences_sample (test.test_ucn.UnicodeNamesTest.test_named_sequences_sample) ... ok
test_strict_error_handling (test.test_ucn.UnicodeNamesTest.test_strict_error_handling) ... ok

----------------------------------------------------------------------
Ran 14 tests in 4.010s

OK (skipped=2)
<sys>:0: ResourceWarning: unclosed <socket.socket [closed] fd=3, family=2, type=1, proto=6>
Object allocated at (most recent call last):
  File "/home/graingert/projects/cpython/Lib/unittest/main.py", lineno 270
    self.result = testRunner.run(self.test)
  File "/home/graingert/projects/cpython/Lib/unittest/runner.py", lineno 240
    test(result)
  File "/home/graingert/projects/cpython/Lib/unittest/suite.py", lineno 84
    return self.run(*args, **kwds)
  File "/home/graingert/projects/cpython/Lib/unittest/suite.py", lineno 122
    test(result)
  File "/home/graingert/projects/cpython/Lib/unittest/suite.py", lineno 84
    return self.run(*args, **kwds)
  File "/home/graingert/projects/cpython/Lib/unittest/suite.py", lineno 122
    test(result)
  File "/home/graingert/projects/cpython/Lib/unittest/suite.py", lineno 84
    return self.run(*args, **kwds)
  File "/home/graingert/projects/cpython/Lib/unittest/suite.py", lineno 122
    test(result)
  File "/home/graingert/projects/cpython/Lib/unittest/case.py", lineno 707
    return self.run(*args, **kwds)
  File "/home/graingert/projects/cpython/Lib/unittest/case.py", lineno 651
    self._callTestMethod(testMethod)
  File "/home/graingert/projects/cpython/Lib/unittest/case.py", lineno 606
    if method() is not None:
  File "/home/graingert/projects/cpython/Lib/test/test_ucn.py", lineno 182
    testdata = support.open_urlresource(url, encoding="utf-8",
  File "/home/graingert/projects/cpython/Lib/test/support/__init__.py", lineno 741
    f = opener.open(url, timeout=INTERNET_TIMEOUT)
  File "/home/graingert/projects/cpython/Lib/urllib/request.py", lineno 489
    response = self._open(req, data)
  File "/home/graingert/projects/cpython/Lib/urllib/request.py", lineno 506
    result = self._call_chain(self.handle_open, protocol, protocol +
  File "/home/graingert/projects/cpython/Lib/urllib/request.py", lineno 466
    result = func(*args)
  File "/home/graingert/projects/cpython/Lib/urllib/request.py", lineno 1348
    return self.do_open(http.client.HTTPConnection, req)
  File "/home/graingert/projects/cpython/Lib/urllib/request.py", lineno 1319
    h.request(req.get_method(), req.selector, req.data, headers,
  File "/home/graingert/projects/cpython/Lib/http/client.py", lineno 1338
    self._send_request(method, url, body, headers, encode_chunked)
  File "/home/graingert/projects/cpython/Lib/http/client.py", lineno 1384
    self.endheaders(body, encode_chunked=encode_chunked)
  File "/home/graingert/projects/cpython/Lib/http/client.py", lineno 1333
    self._send_output(message_body, encode_chunked=encode_chunked)
  File "/home/graingert/projects/cpython/Lib/http/client.py", lineno 1093
    self.send(msg)
  File "/home/graingert/projects/cpython/Lib/http/client.py", lineno 1037
    self.connect()
  File "/home/graingert/projects/cpython/Lib/http/client.py", lineno 1003
    self.sock = self._create_connection(
  File "/home/graingert/projects/cpython/Lib/socket.py", lineno 844
    sock = socket(af, socktype, proto)

CPython versions tested on:

3.14, CPython main branch, 3.13

Operating systems tested on:

No response

Linked PRs

• gh-131807: fix ResourceWarning in test_ucn.py #131808
• [3.13] gh-131807: fix ResourceWarning in test_ucn.py (GH-131808) #131845
• [3.12] gh-131807: fix ResourceWarning in test_ucn.py (GH-131808) #131846