exception: Add exception_msg helper

Signed-off-by: Simon Rozman <simon@rozman.si>

UnitTests/main.cpp

@@ -39,7 +39,7 @@ int main(int, const char *[])
 		return 0;
 	}
 	catch (const std::exception& ex) {
-		std::cerr << ex.what() << " FAIL\n";
+		std::cerr << stdex::exception_msg(ex) << " FAIL\n";
 		return 1;
 	}
 }