pass lazy loading flag into error, to format message based on it

src/errors.js

@@ -1,11 +1,12 @@
 // can't just do InvalidStoreError extends Error
 // because of http://babeljs.io/docs/usage/caveats/#classes
-function InvalidStoreError(reason) {
+function InvalidStoreError(reason, value) {
     const message = `Store is invalid because ${reason}, ` +
         `please delete all data and retry`;
     const instance = Reflect.construct(Error, [message]);
     Reflect.setPrototypeOf(instance, Reflect.getPrototypeOf(this));
     instance.reason = reason;
+    instance.value = value;
     return instance;
 }