There is a new version of lsst_sims available via eups distrib install.  This version is python 3 compliant.  To install it, run either
eups distrib install lsst_sims -t sims
or
eups distrib install lsst_sims -t sims_2_3_4
The DM part of this stack is built against version 13.0.  lsst_sims is not yet compatible with pybind11, which DM recently adopted as their tool for wrapping C++ into python (they formerly to use SWIG).  The next version of lsst_sims ought to be pybind11 compatible, as well.
Note: this stack will not work if you have an astropy version > 1.2.  Hopefully the next version of lsst_sims will be compatible with astropy 1.3.