Adding more descriptive namespace error

(cherry picked from commit a601ae0)

lib/pretender-config.js

@@ -305,8 +305,15 @@ export default class PretenderConfig {
 
           this.unhandledRequest = function (verb, path) {
             path = decodeURI(path);
+            let namespaceError = "";
+            if (this.namespace === "") {
+              namespaceError =
+                  "There is no existing namespace defined. Please define one";
+            } else {
+              namespaceError = `The existing namespace is ${this.namespace}`;
+            }
             assert(
-              `Your app tried to ${verb} '${path}', but there was no route defined to handle this request. Define a route for this endpoint in your routes() config. Did you forget to define a namespace?`
+              `Your app tried to ${verb} '${path}', but there was no route defined to handle this request. Define a route for this endpoint in your routes() config. Did you forget to define a namespace?  ${namespaceError}`
             );
           };
         },