Documentation Issue

[lukesneeringer]

From @bjwatson:

we seem to have a problem with the Python ReadTheDocs: https://docs.google.com/a/google.com/document/d/1JdtcswiBjuuGHub1f-8QCsPjktM_Fp2EGmu5JW6Fyhk/edit?disco=AAAAA6UcdJM
I'm getting blank pages for all of the API-specific documentation: https://google-cloud-python.readthedocs.io/en/latest

[dhermes]

See #3056 and #3025

[bjwatson]

Closing. Duplicates #3025.