we now handle `datum_exc_t` exceptions on the shards (cf. Issue #568)
removed debug print statement in shim.rb
removed useless `datum_exc_t` serialization
removed useless boost::get code
removed useless boost::get code
Fixed unit test for 568
fixing segfault during missing option errors in command-line parsing
fixed silly assert
Merge branch 'mlucy_issue_568' into next
Merge branch 'next' into sam_207