Roundup action fails

[alexdunnjpl]

Checked for duplicates

No - I haven't checked

🐛 Describe the bug

Most-recent registry-sweepers Unstable Assembly action fails due to https://github.com/NASA-PDS/registry-sweepers/actions/runs/7548793144/job/20551562623

Mirrors issue dealt with in https://github.com/NASA-PDS/registry-sweepers/issues/94

 INFO:pds.roundup.assembly:🏎▁▂▃▄▅▆▆▇▇██💨 EXECUTING step _DocsStep
DEBUG:pds.roundup.util:🏃‍♀️ Running «['/usr/local/bin/sphinx-build', '-a', '-b', 'html', 'docs/source', 'docs/build']»
CRITICAL:pds.roundup.util:💥 Process with command line ['/usr/local/bin/sphinx-build', '-a', '-b', 'html', 'docs/source', 'docs/build'] failed with status 2
CRITICAL:pds.roundup.util:🪵 Stdout = «Running Sphinx v3.2.1
»
CRITICAL:pds.roundup.util:📚 Stderr = «
Sphinx version error:
The alabaster extension used by this project needs at least Sphinx v3.4; it therefore cannot be built with this version.
»
Traceback (most recent call last):
  File "/usr/local/lib/python3.9/site-packages/pds/roundup/util.py", line 52, in invoke
    cp = subprocess.run(argv, stdin=subprocess.DEVNULL, capture_output=True, check=True)
  File "/usr/local/lib/python3.9/subprocess.py", line 528, in run
    raise CalledProcessError(retcode, process.args,
subprocess.CalledProcessError: Command '['/usr/local/bin/sphinx-build', '-a', '-b', 'html', 'docs/source', 'docs/build']' returned non-zero exit status 2.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/bin/roundup", line 8, in <module>
    sys.exit(main())
  File "/usr/local/lib/python3.9/site-packages/pds/roundup/main.py", line 119, in main
    _assemblies[args.assembly](context).roundup()
  File "/usr/local/lib/python3.9/site-packages/pds/roundup/assembly.py", line 42, in roundup
    step.execute()
  File "/usr/local/lib/python3.9/site-packages/pds/roundup/_python.py", line 107, in execute
    invoke(['/usr/local/bin/sphinx-build', '-a', '-b', 'html', 'docs/source', 'docs/build'])
  File "/usr/local/lib/python3.9/site-packages/pds/roundup/util.py", line 61, in invoke
    raise InvokedProcessError(ex)
pds.roundup.errors.InvokedProcessError: ('Process %s failed with code %d', ['/usr/local/bin/sphinx-build', '-a', '-b', 'html', 'docs/source', 'docs/build'], 2)

🕵️ Expected behavior

I expect roundup step of unstable assembly to work

📜 To Reproduce

Run an unstable assembly github action

🖥 Environment Info

No response

📚 Version of Software Used

No response

🩺 Test Data / Additional context

No response

🦄 Related requirements

No response

⚙️ Engineering Details

No response