+/** (Deprecated) Generic exception
+ *
+ * An error is defined by a category and a value within that category.
+ *
+ * This used to be a structure for C exceptions but it has been retrofitted
+ * as a C++ exception and some of its data has been moved in the
+ * WithContextException base class. We should deprecate it and replace it
+ * with either C++ different exceptions or `std::system_error` which already
+ * provides this (category + error code) logic.
+ */