Changing PyDict_MINSIZE to 4 causes the following failure:

python -m test.test_packaging
...
Traceback (most recent call last):
  File "/home/mark/python/cpython/Lib/runpy.py", line 160, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/home/mark/python/cpython/Lib/runpy.py", line 73, in _run_code
    exec(code, run_globals)
  File "/home/mark/python/cpython/Lib/test/test_packaging.py", line 5, in <module>
    test_main()
  File "/home/mark/python/cpython/Lib/test/support.py", line 1496, in decorator
    return func(*args)
  File "/home/mark/python/cpython/Lib/packaging/tests/__main__.py", line 18, in test_main
    run_unittest(test_loader.discover(start_dir, top_level_dir=top_dir))
  File "/home/mark/python/cpython/Lib/test/support.py", line 1403, in run_unittest
    _run_suite(suite)
  File "/home/mark/python/cpython/Lib/test/support.py", line 1378, in _run_suite
    raise TestFailed(err)
test.support.TestFailed: Traceback (most recent call last):
  File "/home/mark/python/cpython/Lib/packaging/tests/test_create.py", line 168, in test_convert_setup_py_to_cfg
    """))
AssertionError: '[metadata]\nname = pyxfoil\nversion = 0.2\nsummary = Python bindings for the Xf [truncated]... != '[metadata]\nname = pyxfoil\nversion = 0.2\nsummary = Python bindings for the Xf [truncated]...
  [metadata]
  name = pyxfoil
  version = 0.2
  summary = Python bindings for the Xfoil engine
  download_url = UNKNOWN
  home_page = http://www.python-science.org/project/pyxfoil
  maintainer = André Espaze
  maintainer_email = andre.espaze@logilab.fr
  description = My super Death-scription
         |barbar is now on the public domain,
         |ho, baby !

  [files]
  packages = pyxfoil
      babar
      me
  modules = my_lib
      mymodule
  scripts = my_script
      bin/run
  extra_files = Martinique/Lamentin/dady
      Martinique/Lamentin/mumy
      Martinique/Lamentin/sys
      Martinique/Lamentin/bro
      setup.py
      README
-     pyxfoil/fengine.so
      Pom
      Flora
      Alexander
+     pyxfoil/fengine.so

  resources =
      README.rst = {doc}
      pyxfoil.1 = {man}

Thanks for the report; it was not obvious (due to title/scope change) that there was already one :)  I’m on this.