Fixes #671.

PR checklist:

• Make sure to open an issue as a bug/issue before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
• Ensure the tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)

Re-echoing a comment here - why wasn't this detected earlier, do we have a glitch in the CI pipeline? The PR that caused this was merged more than 3 weeks ago.

I was wondering why we didn't hit this before, but I guess this method is only called during cleanup that isn't usually needed.

Maybe we should write a test for this.

The periodic sample tests for this repo have had 37 straight days. So it's probably not (just) a glitch in the pipeline, it's that no one is watching the results.

So it's probably not (just) a glitch in the pipeline, it's that no one is watching the results.

Where can those be seen, or is that an internal thing?
(as an external maintainer I can only the Kokoro checks here on )