Comment 1 for bug 2009278

There may be two bugs here in reality:
1) non-architecture-specific repositories on the build bases
   - Snapcraft could mangle them to avoid the problem
   - the build bases could have [arch=<>] bits added to the default repos
   - Snapcraft could allow advanced grammar for `package-repositories`

2) Snapcraft holding on to apt caches across parts
   - this may be found to be by design
   - but re-reading the cache in `pull` steps could also help