Had same problem with Perl, turned out that my Linux distribution had some bad characters on the first line of /etc/issue, a dirty quick solution was to delete that first line so I got a hit on a text-string.
Problem is in the SDK (Perl in this case, guess it is the same in Python.
Your reply got me pointed in the right direction and I managed to find a workaround. My employer has a large security blurb in /etc/issue and I guess the API doesn't like it. Rather than changing /etc/issue, I updated the code a bit so it would be able to find my OS. For the benefit of anyone else who finds this, in NaServer.py I changed: