discord.pyのインストールが失敗します

Question

前提

さくらインターネットのスタンダードプランでpythonをこちらの手順でインストールしました。
https://notemite.com/python/python3-on-sakura-rental/

バージョンは手順と同じ通りなのでpython3.9.0です。

実現したいこと

さくらインターネットを使いpythonでdiscord.pyを動かしたいです。
どうすればよいでしょうか。

発生している問題・エラーメッセージ

python3 -m pip install -U "discord.py[voice]"
こちらのコマンドを実行すると以下のようになりインストールができなかったです。

(env) % python3 -m pip install -U "discord.py[voice]"
Collecting discord.py[voice]
  Using cached discord.py-2.0.1-py3-none-any.whl (1.1 MB)
Collecting aiohttp<4,>=3.7.4
  Using cached aiohttp-3.8.1.tar.gz (7.3 MB)
  Installing build dependencies ... done
  Getting requirements to build wheel ... done
  Installing backend dependencies ... done
  Preparing metadata (pyproject.toml) ... error
  error: subprocess-exited-with-error

  × Preparing metadata (pyproject.toml) did not run successfully.
  │ exit code: 1
  ╰─> [74 lines of output]
      *********************
      * Accelerated build *
      *********************
      running dist_info
      creating /var/tmp/pip-modern-metadata-vf7e_moh/aiohttp.egg-info
      writing /var/tmp/pip-modern-metadata-vf7e_moh/aiohttp.egg-info/PKG-INFO
      writing dependency_links to /var/tmp/pip-modern-metadata-vf7e_moh/aiohttp.egg-info/dependency_links.txt
      writing requirements to /var/tmp/pip-modern-metadata-vf7e_moh/aiohttp.egg-info/requires.txt
      writing top-level names to /var/tmp/pip-modern-metadata-vf7e_moh/aiohttp.egg-info/top_level.txt
      writing manifest file '/var/tmp/pip-modern-metadata-vf7e_moh/aiohttp.egg-info/SOURCES.txt'
      reading manifest file '/var/tmp/pip-modern-metadata-vf7e_moh/aiohttp.egg-info/SOURCES.txt'
      reading manifest template 'MANIFEST.in'
      warning: no files found matching 'aiohttp' anywhere in distribution
      warning: no previously-included files matching '*.pyc' found anywhere in distribution
      warning: no previously-included files matching '*.pyd' found anywhere in distribution
      warning: no previously-included files matching '*.so' found anywhere in distribution
      warning: no previously-included files matching '*.lib' found anywhere in distribution
      warning: no previously-included files matching '*.dll' found anywhere in distribution
      warning: no previously-included files matching '*.a' found anywhere in distribution
      warning: no previously-included files matching '*.obj' found anywhere in distribution
      warning: no previously-included files found matching 'aiohttp/*.html'
      no previously-included directories found matching 'docs/_build'
      adding license file 'LICENSE.txt'
      writing manifest file '/var/tmp/pip-modern-metadata-vf7e_moh/aiohttp.egg-info/SOURCES.txt'
      creating '/var/tmp/pip-modern-metadata-vf7e_moh/aiohttp-3.8.1.dist-info'
      Traceback (most recent call last):
        File "/home/itest/work/env/lib/python3.9/site-packages/pip/_vendor/pep517/in_process/_in_process.py", line 363, in <module>
          main()
        File "/home/itest/work/env/lib/python3.9/site-packages/pip/_vendor/pep517/in_process/_in_process.py", line 345, in main
          json_out['return_val'] = hook(**hook_input['kwargs'])
        File "/home/itest/work/env/lib/python3.9/site-packages/pip/_vendor/pep517/in_process/_in_process.py", line 164, in prepare_metadata_for_build_wheel
          return hook(metadata_directory, config_settings)
        File "/var/tmp/pip-build-env-yx9umj6z/overlay/lib/python3.9/site-packages/setuptools/build_meta.py", line 377, in prepare_metadata_for_build_wheel
          self.run_setup()
        File "/var/tmp/pip-build-env-yx9umj6z/overlay/lib/python3.9/site-packages/setuptools/build_meta.py", line 335, in run_setup
          exec(code, locals())
        File "<string>", line 54, in <module>
        File "/var/tmp/pip-build-env-yx9umj6z/overlay/lib/python3.9/site-packages/setuptools/__init__.py", line 87, in setup
          return distutils.core.setup(**attrs)
        File "/var/tmp/pip-build-env-yx9umj6z/overlay/lib/python3.9/site-packages/setuptools/_distutils/core.py", line 185, in setup
          return run_commands(dist)
        File "/var/tmp/pip-build-env-yx9umj6z/overlay/lib/python3.9/site-packages/setuptools/_distutils/core.py", line 201, in run_commands
          dist.run_commands()
        File "/var/tmp/pip-build-env-yx9umj6z/overlay/lib/python3.9/site-packages/setuptools/_distutils/dist.py", line 973, in run_commands
          self.run_command(cmd)
        File "/var/tmp/pip-build-env-yx9umj6z/overlay/lib/python3.9/site-packages/setuptools/dist.py", line 1217, in run_command
          super().run_command(command)
        File "/var/tmp/pip-build-env-yx9umj6z/overlay/lib/python3.9/site-packages/setuptools/_distutils/dist.py", line 992, in run_command
          cmd_obj.run()
        File "/var/tmp/pip-build-env-yx9umj6z/overlay/lib/python3.9/site-packages/setuptools/command/dist_info.py", line 101, in run
          bdist_wheel = self.get_finalized_command('bdist_wheel')
        File "/var/tmp/pip-build-env-yx9umj6z/overlay/lib/python3.9/site-packages/setuptools/_distutils/cmd.py", line 305, in get_finalized_command
          cmd_obj = self.distribution.get_command_obj(command, create)
        File "/var/tmp/pip-build-env-yx9umj6z/overlay/lib/python3.9/site-packages/setuptools/_distutils/dist.py", line 864, in get_command_obj
          klass = self.get_command_class(command)
        File "/var/tmp/pip-build-env-yx9umj6z/overlay/lib/python3.9/site-packages/setuptools/dist.py", line 954, in get_command_class
          self.cmdclass[command] = cmdclass = ep.load()
        File "/var/tmp/pip-build-env-yx9umj6z/overlay/lib/python3.9/site-packages/setuptools/_vendor/importlib_metadata/__init__.py", line 194, in load
          module = import_module(match.group('module'))
        File "/home/itest/local/python/lib/python3.9/importlib/__init__.py", line 127, in import_module
          return _bootstrap._gcd_import(name[level:], package, level)
        File "<frozen importlib._bootstrap>", line 1030, in _gcd_import
        File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
        File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
        File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
        File "<frozen importlib._bootstrap_external>", line 790, in exec_module
        File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
        File "/var/tmp/pip-build-env-yx9umj6z/normal/lib/python3.9/site-packages/wheel/bdist_wheel.py", line 26, in <module>
          from .macosx_libfile import calculate_macosx_platform_tag
        File "/var/tmp/pip-build-env-yx9umj6z/normal/lib/python3.9/site-packages/wheel/macosx_libfile.py", line 41, in <module>
          import ctypes
        File "/home/itest/local/python/lib/python3.9/ctypes/__init__.py", line 8, in <module>
          from _ctypes import Union, Structure, Array
      ModuleNotFoundError: No module named '_ctypes'
      [end of output]

  note: This error originates from a subprocess, and is likely not a problem with pip.
error: metadata-generation-failed

× Encountered error while generating package metadata.
╰─> See above for output.

note: This is an issue with the package mentioned above, not pip.
hint: See above for details.

補足情報（FW/ツールのバージョンなど）

(env) % python3 --version
Python 3.9.0

(env) % pip list
Package    Version
---------- -------
pip        22.2.2
setuptools 65.3.0

Answer 1

ありがとうございます。参考にしてみます。

Answer 2

参考にしているページではconfigureに--with-system-ffiというオプションを指定していますが、
https://docs.python.org/ja/3.9/license.html#libffi
に載っているオプションは--with-system-libffiです。
--with-system-libffiを試してもいいかもしれません。（実際試していないので分かりませんが）