because these classes should not have any side effects. case in point:
the warnings intended to be printed once get printed once per process
which can be quite a few times for parallel simulations with thousands
of cores. This could also be avoided by checking the MPI rank, but
IMHO this is way too much boilerplate code for a feature of questionable
value.
this lead to a compiler warning on gcc 4.8 that this case was already
covered by catching std::exception. Since we did the same in both
branches anyway, these statements were not required...
