feat: update readthedocs build

[gmacario]

📑 Description

Currently Docker image (ubuntu-20.04) used for building the website on https://app.readthedocs.org/ is deprecated and will be removed by 2026-06-01

See https://about.readthedocs.com/blog/2026/03/ubuntu-20-04-deprecated/

Also update Python tool to 3.12 (default for Ubuntu 24.04)

Closes #

✅ Checks

• My pull request adheres to the code style of this project
• My code requires changes to the documentation
• I have updated the documentation as required
• All the tests have passed

ℹ Additional Information

[gmacario]

The PR does not build correctly

From https://app.readthedocs.org/projects/arneis/builds/32042086/

python -m pip install --exists-action=w --no-cache-dir -r docs/requirements.txt  
Collecting alabaster==0.7.12 (from -r docs/requirements.txt (line 1))
  Downloading alabaster-0.7.12-py2.py3-none-any.whl.metadata (2.0 kB)
Collecting attrs==21.4.0 (from -r docs/requirements.txt (line 2))
  Downloading attrs-21.4.0-py2.py3-none-any.whl.metadata (9.8 kB)
Collecting Babel==2.9.1 (from -r docs/requirements.txt (line 3))
  Downloading Babel-2.9.1-py2.py3-none-any.whl.metadata (1.2 kB)
Collecting certifi==2021.10.8 (from -r docs/requirements.txt (line 4))
  Downloading certifi-2021.10.8-py2.py3-none-any.whl.metadata (3.0 kB)
Collecting charset-normalizer==2.0.10 (from -r docs/requirements.txt (line 5))
  Downloading charset_normalizer-2.0.10-py3-none-any.whl.metadata (11 kB)
Collecting docutils==0.17.1 (from -r docs/requirements.txt (line 6))
  Downloading docutils-0.17.1-py2.py3-none-any.whl.metadata (2.9 kB)
Collecting idna==3.3 (from -r docs/requirements.txt (line 7))
  Downloading idna-3.3-py3-none-any.whl.metadata (9.8 kB)
Collecting imagesize==1.3.0 (from -r docs/requirements.txt (line 8))
  Downloading imagesize-1.3.0-py2.py3-none-any.whl.metadata (1.4 kB)
Collecting importlib-metadata==4.10.1 (from -r docs/requirements.txt (line 9))
  Downloading importlib_metadata-4.10.1-py3-none-any.whl.metadata (4.0 kB)
Collecting Jinja2==3.0.3 (from -r docs/requirements.txt (line 10))
  Downloading Jinja2-3.0.3-py3-none-any.whl.metadata (3.5 kB)
Collecting markdown-it-py==2.0.0 (from -r docs/requirements.txt (line 11))
  Downloading markdown_it_py-2.0.0-py3-none-any.whl.metadata (6.9 kB)
Collecting MarkupSafe==2.0.1 (from -r docs/requirements.txt (line 12))
  Downloading MarkupSafe-2.0.1.tar.gz (18 kB)
  Installing build dependencies: started
  Installing build dependencies: finished with status 'done'
  Getting requirements to build wheel: started
  Getting requirements to build wheel: finished with status 'done'
  Preparing metadata (pyproject.toml): started
  Preparing metadata (pyproject.toml): finished with status 'done'
Collecting mdit-py-plugins==0.3.0 (from -r docs/requirements.txt (line 13))
  Downloading mdit_py_plugins-0.3.0-py3-none-any.whl.metadata (2.8 kB)
Collecting mdurl==0.1.0 (from -r docs/requirements.txt (line 14))
  Downloading mdurl-0.1.0-py3-none-any.whl.metadata (4.7 kB)
Collecting myst-parser==0.16.1 (from -r docs/requirements.txt (line 15))
  Downloading myst_parser-0.16.1-py3-none-any.whl.metadata (5.1 kB)
Collecting packaging==21.3 (from -r docs/requirements.txt (line 16))
  Downloading packaging-21.3-py3-none-any.whl.metadata (15 kB)
Collecting Pygments==2.11.2 (from -r docs/requirements.txt (line 17))
  Downloading Pygments-2.11.2-py3-none-any.whl.metadata (1.5 kB)
Collecting pyparsing==3.0.6 (from -r docs/requirements.txt (line 18))
  Downloading pyparsing-3.0.6-py3-none-any.whl.metadata (4.2 kB)
Collecting pytz==2021.3 (from -r docs/requirements.txt (line 19))
  Downloading pytz-2021.3-py2.py3-none-any.whl.metadata (21 kB)
Collecting PyYAML==6.0 (from -r docs/requirements.txt (line 20))
  Downloading PyYAML-6.0.tar.gz (124 kB)
  Installing build dependencies: started
  Installing build dependencies: finished with status 'done'
  Getting requirements to build wheel: started
  Getting requirements to build wheel: finished with status 'error'
  error: subprocess-exited-with-error
  
  × Getting requirements to build wheel did not run successfully.
  │ exit code: 1
  ╰─> [67 lines of output]
      /tmp/pip-build-env-1wek3rq3/overlay/lib/python3.12/site-packages/wheel/bdist_wheel.py:4: FutureWarning: The 'wheel' package is no longer the canonical location of the 'bdist_wheel' command, and will be removed in a future release. Please update to setuptools v70.1 or later which contains an integrated version of this command.
        warn(
      /tmp/pip-build-env-1wek3rq3/overlay/lib/python3.12/site-packages/setuptools/dist.py:765: SetuptoolsDeprecationWarning: License classifiers are deprecated.
      !!
      
              ********************************************************************************
              Please consider removing the following classifiers in favor of a SPDX license expression:
      
              License :: OSI Approved :: MIT License
      
              See https://packaging.python.org/en/latest/guides/writing-pyproject-toml/#license for details.
              ********************************************************************************
      
      !!
        self._finalize_license_expression()
      running egg_info
      writing lib/PyYAML.egg-info/PKG-INFO
      writing dependency_links to lib/PyYAML.egg-info/dependency_links.txt
      writing top-level names to lib/PyYAML.egg-info/top_level.txt
      Traceback (most recent call last):
        File "/home/docs/checkouts/readthedocs.org/user_builds/arneis/envs/382/lib/python3.12/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 389, in <module>
          main()
        File "/home/docs/checkouts/readthedocs.org/user_builds/arneis/envs/382/lib/python3.12/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 373, in main
          json_out["return_val"] = hook(**hook_input["kwargs"])
                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/home/docs/checkouts/readthedocs.org/user_builds/arneis/envs/382/lib/python3.12/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 143, in get_requires_for_build_wheel
          return hook(config_settings)
                 ^^^^^^^^^^^^^^^^^^^^^
        File "/tmp/pip-build-env-1wek3rq3/overlay/lib/python3.12/site-packages/setuptools/build_meta.py", line 333, in get_requires_for_build_wheel
          return self._get_build_requires(config_settings, requirements=[])
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/tmp/pip-build-env-1wek3rq3/overlay/lib/python3.12/site-packages/setuptools/build_meta.py", line 301, in _get_build_requires
          self.run_setup()
        File "/tmp/pip-build-env-1wek3rq3/overlay/lib/python3.12/site-packages/setuptools/build_meta.py", line 317, in run_setup
          exec(code, locals())
        File "<string>", line 288, in <module>
        File "/tmp/pip-build-env-1wek3rq3/overlay/lib/python3.12/site-packages/setuptools/__init__.py", line 117, in setup
          return distutils.core.setup(**attrs)  # type: ignore[return-value]
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/tmp/pip-build-env-1wek3rq3/overlay/lib/python3.12/site-packages/setuptools/_distutils/core.py", line 186, in setup
          return run_commands(dist)
                 ^^^^^^^^^^^^^^^^^^
        File "/tmp/pip-build-env-1wek3rq3/overlay/lib/python3.12/site-packages/setuptools/_distutils/core.py", line 202, in run_commands
          dist.run_commands()
        File "/tmp/pip-build-env-1wek3rq3/overlay/lib/python3.12/site-packages/setuptools/_distutils/dist.py", line 1000, in run_commands
          self.run_command(cmd)
        File "/tmp/pip-build-env-1wek3rq3/overlay/lib/python3.12/site-packages/setuptools/dist.py", line 1107, in run_command
          super().run_command(command)
        File "/tmp/pip-build-env-1wek3rq3/overlay/lib/python3.12/site-packages/setuptools/_distutils/dist.py", line 1019, in run_command
          cmd_obj.run()
        File "/tmp/pip-build-env-1wek3rq3/overlay/lib/python3.12/site-packages/setuptools/command/egg_info.py", line 312, in run
          self.find_sources()
        File "/tmp/pip-build-env-1wek3rq3/overlay/lib/python3.12/site-packages/setuptools/command/egg_info.py", line 320, in find_sources
          mm.run()
        File "/tmp/pip-build-env-1wek3rq3/overlay/lib/python3.12/site-packages/setuptools/command/egg_info.py", line 542, in run
          self.add_defaults()
        File "/tmp/pip-build-env-1wek3rq3/overlay/lib/python3.12/site-packages/setuptools/command/egg_info.py", line 580, in add_defaults
          sdist.add_defaults(self)
        File "/tmp/pip-build-env-1wek3rq3/overlay/lib/python3.12/site-packages/setuptools/command/sdist.py", line 110, in add_defaults
          super().add_defaults()
        File "/tmp/pip-build-env-1wek3rq3/overlay/lib/python3.12/site-packages/setuptools/_distutils/command/sdist.py", line 245, in add_defaults
          self._add_defaults_ext()
        File "/tmp/pip-build-env-1wek3rq3/overlay/lib/python3.12/site-packages/setuptools/_distutils/command/sdist.py", line 330, in _add_defaults_ext
          self.filelist.extend(build_ext.get_source_files())
                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "<string>", line 204, in get_source_files
      AttributeError: 'build_ext' object has no attribute 'cython_sources'
      [end of output]
  
  note: This error originates from a subprocess, and is likely not a problem with pip.
ERROR: Failed to build 'PyYAML' when getting requirements to build wheel

[gmacario]

TODO: Should also update https://github.com/B-AROL-O/ARNEIS/blob/main/docs/requirements.txt