I ran into an issue the other day when non ascii characters were in the Customer name. I tracked down the issue and put out a bug fix release for that today. You can read more about the bug here. Coming up in the next couple of weeks for version 0.5 will be support for vCloud Director. To update to the latest version of thunderhead simply run:
pip install -U thunderhead
And this will update you from 0.4 to 0.4.1 If you have any questions or need any help please feel free to reach out to me.