copyPackage fails when source is not available in source suite

[Iain Lane]

proposed-migration is trying to migrate the riscv64 build of this package:

laney@nightingale> rmadison -shirsute,hirsute-proposed -S kineticstools
 kineticstools | 0.6.1+git20200325.3558942+dfsg-1 | hirsute/universe | source, all
 kineticstools-data | 0.6.1+git20200325.3558942+dfsg-1 | hirsute/universe | all
 python3-kineticstools | 0.6.1+git20200325.3558942+dfsg-1 | hirsute/universe | amd64, arm64, armhf, ppc64el
 python3-kineticstools | 0.6.1+git20200325.3558942+dfsg-1 | hirsute-proposed/universe | riscv64

using copyPackage. It is failing to do so though, with:

copyPackage kineticstools/0.6.1+git20200325.3558942+dfsg-1/riscv64: b'kineticstools is not published in Primary Archive for Ubuntu.'

This ought to have worked, I think. Theory is that the lack of the source build in the source suite is what's tripping this up.