TypeError: 'generator' object is not reversible

[EnricoCorsaro]

Describe the bug

I cannot compile anymore my online readthedocs linked to my github repo. I can confirm that I am able to compile sphinx successfully in my local machine (I am using a Mac OS v. 11.6), so the problem should not rely on my actual documentation, but it appears to be a bug of the online readthedocs compiling system.

Exception occurred:
File "/home/docs/checkouts/readthedocs.org/user_builds/famed/envs/latest/lib/python3.7/site-packages/sphinx/util/nodes.py", line 94, in apply_source_workaround
for classifier in reversed(node.parent.traverse(nodes.classifier)):
TypeError: 'generator' object is not reversible

How to Reproduce

$ git clone --no-single-branch --depth 50 https://github.com/EnricoCorsaro/FAMED.git .
$ git checkout --force origin/master
$ git clean -d -f -f
$ python3.7 -mvirtualenv /home/docs/checkouts/readthedocs.org/user_builds/famed/envs/latest
$ /home/docs/checkouts/readthedocs.org/user_builds/famed/envs/latest/bin/python -m pip install --upgrade --no-cache-dir pip setuptools
$ /home/docs/checkouts/readthedocs.org/user_builds/famed/envs/latest/bin/python -m pip install --upgrade --no-cache-dir mock==1.0.1 pillow==5.4.1 alabaster>=0.7,<0.8,!=0.7.5 commonmark==0.8.1 recommonmark==0.5.0 sphinx<2 sphinx-rtd-theme<0.5 readthedocs-sphinx-ext<2.2
$ cat docs/source/conf.py
$ /home/docs/checkouts/readthedocs.org/user_builds/famed/envs/latest/bin/python -m sphinx -T -b html -d _build/doctrees -D language=en . _build/html

Expected behavior

Just that the compilation could run smoothly, with only warning messages at most.

Your project

https://readthedocs.org/projects/famed/

Screenshots

I attach the full log of the compilation.
sphinx_error.txt

OS

GitHub repo

Python version

3.7

Sphinx version

1.8.5

Sphinx extensions

No response

Extra tools

No response

Additional context

https://famed.readthedocs.io/en/latest/

[astrojuanlu]

See #9811, #9810, #9809, #9727, #9788, readthedocs/readthedocs.org#8616 , readthedocs/readthedocs.org#8618, readthedocs/readthedocs.org#8640, readthedocs/readthedocs.org#8642. You can solve this by capping docutils to <0.18 in your requirements. More information here: https://blog.readthedocs.com/build-errors-docutils-0-18/