Add missing RTD configuration file, which is obligatory today

[amotl]

Problem

It looks like the RTD configuration file was missing. It was optional before, but is obligatory today.

References

• Documentation: Add page about enumerating use cases #487 (comment)

[amotl]

@martindurant: You said you've enabled the RTD feature to run on pull requests.

-- https://app.readthedocs.org/dashboard/streamz/edit/

However, it is currently not showing up within the GHA PR builder widget (below). Well, maybe this patch needs to be merged before things start working this way, we'll see. In this spirit, I haven't been able to validate the patch / configuration file yet, so you might need to go into a quick trial-and-error cycle at your disposal, if it doesn't work out of the box.

[martindurant]

Understood. That is indeed the button I clicked, so we'll see.

[martindurant]

The build still fails, but now complaining that streamz itself is not installed:

Traceback (most recent call last):
  | File "/home/docs/checkouts/readthedocs.org/user_builds/streamz/envs/latest/lib/python3.14/site-packages/sphinx/config.py", line 601, in eval_config_file
  | exec(code, namespace)  # NoQA: S102
  | ~~~~^^^^^^^^^^^^^^^^^
  | File "/home/docs/checkouts/readthedocs.org/user_builds/streamz/checkouts/latest/docs/source/conf.py", line 59, in <module>
  | import streamz
  | ModuleNotFoundError: No module named 'streamz'
  |  
  | The above exception was the direct cause of the following exception:
  |  
  | Traceback (most recent call last):
  | File "/home/docs/checkouts/readthedocs.org/user_builds/streamz/envs/latest/lib/python3.14/site-packages/sphinx/cmd/build.py", line 414, in build_main
  | app = Sphinx(
  | srcdir=args.sourcedir,
  | ...<14 lines>...
  | exception_on_warning=args.exception_on_warning,
  | )
  | File "/home/docs/checkouts/readthedocs.org/user_builds/streamz/envs/latest/lib/python3.14/site-packages/sphinx/application.py", line 266, in __init__
  | self.config = Config.read(self.confdir, confoverrides or {}, self.tags)
  | ~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  | File "/home/docs/checkouts/readthedocs.org/user_builds/streamz/envs/latest/lib/python3.14/site-packages/sphinx/config.py", line 357, in read
  | namespace = eval_config_file(filename, tags)
  | File "/home/docs/checkouts/readthedocs.org/user_builds/streamz/envs/latest/lib/python3.14/site-packages/sphinx/config.py", line 616, in eval_config_file
  | raise ConfigError(msg % traceback.format_exc()) from exc
  | sphinx.errors.ConfigError: There is a programmable error in your configuration file:
  |  
  | Traceback (most recent call last):
  | File "/home/docs/checkouts/readthedocs.org/user_builds/streamz/envs/latest/lib/python3.14/site-packages/sphinx/config.py", line 601, in eval_config_file
  | exec(code, namespace)  # NoQA: S102
  | ~~~~^^^^^^^^^^^^^^^^^
  | File "/home/docs/checkouts/readthedocs.org/user_builds/streamz/checkouts/latest/docs/source/conf.py", line 59, in <module>
  | import streamz
  | ModuleNotFoundError: No module named 'streamz'
  |  

[amotl]

Thank you. I will try to compensate. I wasn't aware that it also needs the package itself for generating API docs, but well, I could have seen it when looking more closely ;].

-- https://streamz.readthedocs.io/en/latest/api.html