I'm using the default json backend and expect that I don't need to use pymongo or sqlalchemy (although in fact I will later be using sqlalchemy). When importing from backends all the different backends are made available. If you don't have pymongo installed it ought to do nothing and the module should not be available. I see you have some code for that already but it isn't hooked up. Can you please fix this? Thanks.
pymongo ImportError fails silently #32