message: Print a warning when encountering unknown tags in the xml spec instead of aborting with an exception.
diff: @@ -971,8 +971,7 @@ void checkElements(std::vector<tinyxml2::XMLElement const*> const& elements, std
  std::stringstream ss;
  ss << e->GetLineNum();
  std::string lineNumber = ss.str();
  - assert(false);
  - throw std::runtime_error("Spec error on line " + lineNumber + ": unexpected element value <" + e->Value() + ">");
  + std::cerr << "Unknown element in spec on line: " << lineNumber << " " << e->Value() << std::endl;
  }
  }
  }
  @@ -5094,7 +5093,7 @@ int main( int argc, char **argv )
  {
  std::stringstream lineNumber;
  lineNumber << child->GetLineNum();
  - throw std::runtime_error(std::string("unknown tag ") + value + " at line number:" + lineNumber.str());
  + std::cerr << "Unhandled tag " << value << " at line number: " << lineNumber.str() << std::endl;
  }
  }
  