If a session isn't created properly we don't try to save it.
If a session isn't created properly we don't try to save it.

This happens when we have an unhandled http error generated by
tornado. We won't generate the error right now and log a waning
about the issue.

Fixes: #241

piraz/firenado,candango/firenado,piraz/firenado,candango/firenado,piraz/firenado,candango/firenado