For a number of days the ReadTheDocs builds are failing and I don't know why.

The errors make no sense to me. They don't tell me which of the docs is bad nor why.

The things that have changed over the past weeks have been that I'm using my markdown editor in a way that directly integrated into GitHub. And I have been adding repl.it recipe iframes into the Cookbook. I don't think the readme has any yet.

I don't think it's the iframes because they are up and running in the current working Cookbook located here
http://cookbook.PySimpleGUI.org

Readme is here:
http://www.PySimpleGUI.org

Any help would be greatly appreciated!!!

Here's an example build:
https://readthedocs.org/projects/pysimplegui/builds/8589243/

Build #8589243
latest (1eb3c26878e321867fb1dc28d94353d2087fed3f)
Build failed
git clone --no-single-branch --depth 50 https://github.com/PySimpleGUI/PySimpleGUI .
git checkout --force origin/master
git clean -d -f -f
python3.7 -mvirtualenv --no-site-packages --no-download /home/docs/checkouts/readthedocs.org/user_builds/pysimplegui/envs/latest
/home/docs/checkouts/readthedocs.org/user_builds/pysimplegui/envs/latest/bin/python -m pip install --upgrade --cache-dir /home/docs/checkouts/readthedocs.org/user_builds/pysimplegui/.cache/pip pip
/home/docs/checkouts/readthedocs.org/user_builds/pysimplegui/envs/latest/bin/python -m pip install --upgrade --cache-dir /home/docs/checkouts/readthedocs.org/user_builds/pysimplegui/.cache/pip Pygments==2.2.0 setuptools<40 docutils==0.13.1 mock==1.0.1 pillow==2.6.1 alabaster>=0.7,<0.8,!=0.7.5 commonmark==0.5.4 recommonmark==0.4.0 mkdocs==0.17.3
cat mkdocs.yml
python /home/docs/checkouts/readthedocs.org/user_builds/pysimplegui/envs/latest/bin/mkdocs build --clean --site-dir _build/html --config-file /home/docs/checkouts/readthedocs.org/user_builds/pysimplegui/checkouts/latest/mkdocs.yml
INFO    -  Cleaning site directory 
INFO    -  Building documentation to directory: /home/docs/checkouts/readthedocs.org/user_builds/pysimplegui/checkouts/latest/_build/html 
Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/pysimplegui/envs/latest/lib/python3.7/site-packages/mkdocs/nav.py", line 337, in _follow
    raise StopIteration
StopIteration

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/pysimplegui/envs/latest/bin/mkdocs", line 10, in <module>
    sys.exit(cli())
  File "/home/docs/checkouts/readthedocs.org/user_builds/pysimplegui/envs/latest/lib/python3.7/site-packages/click/core.py", line 764, in __call__
    return self.main(*args, **kwargs)
  File "/home/docs/checkouts/readthedocs.org/user_builds/pysimplegui/envs/latest/lib/python3.7/site-packages/click/core.py", line 717, in main
    rv = self.invoke(ctx)
  File "/home/docs/checkouts/readthedocs.org/user_builds/pysimplegui/envs/latest/lib/python3.7/site-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/docs/checkouts/readthedocs.org/user_builds/pysimplegui/envs/latest/lib/python3.7/site-packages/click/core.py", line 956, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/docs/checkouts/readthedocs.org/user_builds/pysimplegui/envs/latest/lib/python3.7/site-packages/click/core.py", line 555, in invoke
    return callback(*args, **kwargs)
  File "/home/docs/checkouts/readthedocs.org/user_builds/pysimplegui/envs/latest/lib/python3.7/site-packages/mkdocs/__main__.py", line 156, in build_command
    ), dirty=not clean)
  File "/home/docs/checkouts/readthedocs.org/user_builds/pysimplegui/envs/latest/lib/python3.7/site-packages/mkdocs/commands/build.py", line 282, in build
    build_pages(config, dirty=dirty)
  File "/home/docs/checkouts/readthedocs.org/user_builds/pysimplegui/envs/latest/lib/python3.7/site-packages/mkdocs/commands/build.py", line 213, in build_pages
    site_navigation = nav.SiteNavigation(config)
  File "/home/docs/checkouts/readthedocs.org/user_builds/pysimplegui/envs/latest/lib/python3.7/site-packages/mkdocs/nav.py", line 44, in __init__
    config, self.url_context)
  File "/home/docs/checkouts/readthedocs.org/user_builds/pysimplegui/envs/latest/lib/python3.7/site-packages/mkdocs/nav.py", line 392, in _generate_site_navigation
    config_line, url_context, config):
RuntimeError: generator raised StopIteration