Mis-leading error message on missing submodule in verification of s2n-tls

[rod-chapman]

Attempting to run all the proofs of s2n-tls locally, I got:

proofs$ ./run-cbmc-proofs.py --summarize

For your convenience, the output of this run will be symbolically linked to  /home/ubuntu/s2n/s2n-tls-5/tests/cbmc/proofs/output/latest/html/index.html 

Configuring CBMC proofs: 163 / 163
CRITICAL:root:Failed to configure the following proofs:
/home/ubuntu/s2n/s2n-tls-5/tests/cbmc/proofs/s2n_hash_new
...

and was somewhat confused as to where I had gone wrong. It turns out I had failed to initialize GIT submodules for the s2n-tls repo following a fresh clone of the repo.

A better error message, along the lines of:

CRITICAL:required Git submodule XXX is missing
CRITICAL:please run 'git submodule update --init'

or similar would be a big help for newbies.