If the version file is empty, complain.
If the version file is empty, complain.

We *could* work around this, but I don't want to mask bugs in the build
system.

Signed-off-by: Zack Cerza <d7cdf09fc0f0426e98c9978ee42da5d61fa54986@redhat.com>

dmick/teuthology,ceph/teuthology,tchaikov/teuthology,zhouyuan/teuthology,dmick/teuthology,ceph/teuthology,dmick/teuthology,michaelsevilla/teuthology,robbat2/teuthology,SUSE/teuthology,caibo2014/teuthology,ktdreyer/teuthology,robbat2/teuthology,t-miyamae/teuthology,tchaikov/teuthology,dreamhost/teuthology,yghannam/teuthology,yghannam/teuthology,SUSE/teuthology,SUSE/teuthology,ivotron/teuthology,t-miyamae/teuthology,ivotron/teuthology,dreamhost/teuthology,caibo2014/teuthology,michaelsevilla/teuthology,zhouyuan/teuthology,ktdreyer/teuthology