Not trivial, but there's a Python wrapper available:
Re:Bayesian Logic Programming
by data_scientist on Friday December 18, 2015 @08:11AM
(#10758221)
PyMC 3 implements HMC. It is still in beta but quite stable
If you're interested: http://pymc-devs.github.io/pymc3/
PyMC3 uses Theano to create a compute graph of the model which then gets compiled to C. Moreover, it gives us the gradient for free so that HMC and NUTS can be used which work models of high complexity.
I use it in production, despite it still being beta. We're close to the first stable release but there are still some small kinks to figure out.
Disclaimer: I'm a co-developer.
How easy would the transition to PyStan be?