I tried issue18383_remove_dups_and_test.patch, but it doesn’t seem to fix the problem, and causes new test failures and warnings. Let me know if you want more info. Existing messages that I thought this was meant to fix:

[372/393/5] test_warnings
/media/disk/home/proj/python/cpython/Lib/test/test_warnings.py:100: UserWarning: FilterTests.test_ignore_after_default
  self.module.warn(message, UserWarning)
/media/disk/home/proj/python/cpython/Lib/test/test_warnings.py:100: UserWarning: FilterTests.test_ignore_after_default
  self.module.warn(message, UserWarning)
Warning -- warnings.filters was modified by test_warnings
[. . .]
1 test altered the execution environment:
    test_warnings

Three new failures:

[ 12/393/1] test___all__
test test___all__ failed -- Traceback (most recent call last):
  File "/media/disk/home/proj/python/cpython/Lib/test/test___all__.py", line 105, in test_all
    self.check_all(modname)
  File "/media/disk/home/proj/python/cpython/Lib/test/test___all__.py", line 28, in check_all
    raise FailedImport(modname)
  File "/media/disk/home/proj/python/cpython/Lib/contextlib.py", line 66, in __exit__
    next(self.gen)
  File "/media/disk/home/proj/python/cpython/Lib/test/support/__init__.py", line 1124, in _filterwarnings
    raise AssertionError("unhandled warning %s" % reraise[0])
AssertionError: unhandled warning {message : DeprecationWarning('stat_float_times() is deprecated',), category : 'DeprecationWarning', filename : '/media/disk/home/proj/python/cpython/Lib/test/test_os.py', lineno : 75, line : None}
[. . .]
[147/393/3] test_global
test test_global failed -- multiple errors occurred; run in verbose mode for details
[. . .]
[240/393/5] test_pkgutil
test test_pkgutil failed -- Traceback (most recent call last):
  File "/media/disk/home/proj/python/cpython/Lib/test/test_pkgutil.py", line 327, in test_importer_deprecated
    x = pkgutil.ImpImporter("")
  File "/media/disk/home/proj/python/cpython/Lib/contextlib.py", line 66, in __exit__
    next(self.gen)
  File "/media/disk/home/proj/python/cpython/Lib/test/support/__init__.py", line 1124, in _filterwarnings
    raise AssertionError("unhandled warning %s" % reraise[0])
AssertionError: unhandled warning {message : PendingDeprecationWarning("the imp module is deprecated in favour of importlib; see the module's documentation for alternative uses",), category : 'PendingDeprecationWarning', filename : '/media/disk/home/proj/python/cpython/Lib/importlib/_bootstrap.py', lineno : 321, line : None}
[. . .]
5 tests failed:
    test___all__ test_distutils test_gdb test_global test_pkgutil

(Ignore distutils and GDB; they normally fail for me.) New warnings, though I suspect they may be a side effect and not entirely the fault of the patch:

[ 18/393/1] test_unittest
[163/393/4] test_imp
[169/393/4] test_importlib
[205/393/4] test_modulefinder
[220/393/4] test_os
[241/393/5] test_platform
[329/393/5] test_threaded_import
[354/393/5] test_unicode