message: Add optional except to action_trace
diff: @@ -37,6 +37,7 @@ namespace eosio { namespace chain {
  block_timestamp_type block_time;
  fc::optional<block_id_type> producer_block_id;
  flat_set<account_delta> account_ram_deltas;
  + fc::optional<fc::exception> except;
  };
  struct action_trace : public base_action_trace {
  @@ -71,7 +72,7 @@ FC_REFLECT( eosio::chain::account_delta,
  FC_REFLECT( eosio::chain::base_action_trace,
  (receipt)(act)(context_free)(elapsed)(cpu_usage)(console)(total_cpu_usage)(trx_id)
  - (block_num)(block_time)(producer_block_id)(account_ram_deltas) )
  + (block_num)(block_time)(producer_block_id)(account_ram_deltas)(except) )
  FC_REFLECT_DERIVED( eosio::chain::action_trace,
  (eosio::chain::base_action_trace), (inline_traces) )
  