Explicit exception class constructor

Author: Petr Bauch

src/util/exception_utils.h

@@ -86,7 +86,7 @@ class incorrect_goto_program_exceptiont : public cprover_exception_baset
   incorrect_goto_program_exceptiont(
     std::string message,
     source_locationt source_location);
-  incorrect_goto_program_exceptiont(std::string message);
+  explicit incorrect_goto_program_exceptiont(std::string message);
   std::string what() const override;
 
 private: