When building equuleus with local packages, apt-get will fail with 'GPG error: ... NO_PUBKEY'. This is a bug in live-build that has existed for a while, but for apt version < 1.5 (jessie, stretch), gave a warning, not an error. Fix available at
https://salsa.debian.org/jestabro-guest/live-build/commits/keys-fix
Patch will be added to Dockerfile until merged or subsumed in upstream.