I was able to reproduce your error on my system. Dug into it a bit with the debugger, and I found that the non-reference object being blessed is this string:
'<hyperdex.client.Client object at 0x7fa3f1c0c560>'
My guess is that it's a bug in Inline::Python
's conversion magic or something unexpected in the Hyperdex libary. The Python object is being created properly, but somewhere it's been converted to a string representation. I really don't know enough Python to hazard a guess as to what's really going on here.
Might be worth filing a bug report for Inline-Python. The Python library Hyperdex installs is a shared library file, not a traditional .py or .pyc module, and I wonder if that perhaps has something to do with it. At least you already have a work-around.