Pybind11 does not currently support translation of custom exceptions. This ticket tracks work done on upstream pybind11 (internal fork https://github.com/lsst-dm/pybind11-1) to implement this functionality. It should support functionality equivalent to (but not necessarily with the same API) as Boost Python exception translators (http://www.boost.org/doc/libs/1_61_0/libs/python/doc/html/reference/high_level_components/boost_python_exception_translato.html).