I was installing gcc when I lost my network connection to the server. I assume there's an incomplete build around.
So currently I have:
$ spack install gcc
==> gcc is already installed in /xfs1/eschnetter/src/spack/opt/spack/linux-x86_64/gcc-4.9.2/gcc-5.2.0-s2elgk7nmbeuiosmp5xuawinugiej2an.
$ spack uninstall gcc
==> Error: gcc does not match any installed packages.
$ spack find gcc
==> 0 installed packages.