Unable to renew. Errors about "not a FQDN"

@ebel, @bmw told me that this is an effect of a deliberate feature: if certbot crashes early enough that it couldn’t set up logging in /var/log, it will save its crash log into the current directory in order to avoid having to print a Python traceback.

I guess the benefits of this can be questioned in the kind of situation you encountered, but it seems like it could be useful to people in other circumstances.