Just to let you know: ubuntu-core-libs and ubuntu-core-libs-dev have
been removed from the archive.
After investigating and asking around, it could not be ascertained
whether there was anything left to make use of it, and it appeared to
be out of date anyway (for example, recommending net-tools, which
we've replaced with iproute2 just about everywhere). Since it's early
in the cycle, removal was picked as the best course of action to find
out if there were any consumers of that package that were missed.
If you run into issues caused by this, please let us know via a bug in
Launchpad against ubuntu-core-meta, so that the situation can be