Replace global std::string
Replace global std::string

Fix message with global std::strings due to possibly resulting in an
exception being thrown outside of the program flow, which can't be
caught.

https://www.securecoding.cert.org/confluence/display/cplusplus/ERR58-CPP.+Constructors+of+objects+with+static+or+thread+storage+duration+must+not+throw+exceptions

important-business/engine,important-business/engine