Okay, it was in 4.4 that I removed CvDiplomacyInterface.py from BUG entirely. I added a feature to BugUtil that allows me to add/change functions from BTS modules from Python, i.e. without supplying a modified file.
That means you should leave it in since RevDCM is based on 4.3. In that case, I have no idea why you'd get that error. When that error happens again, please post PythonDbg.log so I can see what's happening at the same time, hopefully the cause.