message: Add dbg msg to validation in unsafeCreateBlock
  Created blocks are stateless validated in debug mode.
  The assertion was accomplished with the detailed debug messages.
diff: #include "backend/protobuf/proto_block_factory.hpp"
  +#include <sstream>
  +
  #include <boost/assert.hpp>
  -#include <iostream>
  #include "backend/protobuf/block.hpp"
  using namespace shared_model;
  @@ -64,9 +65,14 @@ ProtoBlockFactory::unsafeCreateBlock(
  bool block_is_stateless_valid =
  not(proto_block_validation_result.hasErrors()
  or interface_block_validation_result.hasErrors());
  - BOOST_ASSERT_MSG(block_is_stateless_valid,
  - "ProtoBlockFactory has created stateless invalid block");
  -
  + std::stringstream validaton_results;
  + validaton_results << "ProtoBlockFactory has created stateless invalid block: "
  + << "Proto validator response: "
  + << proto_block_validation_result.reason()
  + << "; Interface validator response: "
  + << interface_block_validation_result.reason() << ";"
  + << std::endl;
  + BOOST_ASSERT_MSG(block_is_stateless_valid, validaton_results.str().c_str());
  return model_proto_block;
  }
  