Unable to locate package nginx

[hubmeister]

When I run the command:
/home/vagrant/packer build template.json
near the bottom of page 52, I get the error:
--------------------------error-------------------------------------------------------------------
docker: E: Unable to locate package nginx
==> docker: Killing the container: 2b2cf07df7618b502f0169a3b80771602265cf3252f312508a0214c195aba336
Build 'docker' errored: Script exited with non-zero exit status: 100
--------------------------end error-------------------------------------------------------------------
when the bootstrap.sh script runs.
I've done a seaarch:
apt-cache search nginx
and nginx is found in the repository