+ *
+ * This function returns UCI_ERR_NOTFOUND if the package specified in the tuple
+ * string cannot be found. Otherwise it will return UCI_OK.
+ *
+ * Note that failures in looking up other parts, if they are also specfied,
+ * including section and option, will also have a return value UCI_OK but with
+ * ptr->flags * UCI_LOOKUP_COMPLETE not set.