Tracing this all the way up the stack I see tha the getGroups method
receives a guid value of set([None]), but this is not caught as I think
maybe it should be on line 675
if guids is None:
But because I am not super familar with this application and have
limited familiarity with python I am not sure if this indicates an issue
with my config, my environment, or the code.
The LDAP directory is incredibly flexible, and can be coerced to do various insane things by setting up mappings incorrectly. Having a copy of your caldavd.plist would be helpful when diagnosing this error. (Actually having a copy of your entire directory along with that would be even more useful, but I presume that isn't possible ;-)).