scheduler: experimental: rules extract failed with exit code 1

In experimental, I've occasionally see this error message (here from hipsparse):

43s blame: hipsparse
43s badpkg: rules extract failed with exit code 1
43s autopkgtest [04:01:29]: ERROR: erroneous package: rules extract failed with exit code 1

Simply re-triggering through the UI fixes this, so I assume that this some sort of Archive sync issue.