Add note in the writing-e2e-tests doc

Author: pratikjagrut

doc/test-framework/writing-e2e-tests.md

@@ -250,8 +250,9 @@ $ operator-sdk test local ./test/e2e --namespace operator-test
 
 To run the operator itself locally during the tests instead of starting a deployment in the cluster, you can use the
 `--up-local` flag. This mode will still create global resources, but by default will not create any in-cluster namespaced
-resources unless the user specifies one through the `--namespaced-manifest` flag. (Note: the `--up-local` flag requires
-the `--namespace` flag):
+resources unless the user specifies one through the `--namespaced-manifest` flag.
+
+**NOTE**: The `--up-local` flag requires the `--namespace` flag and the command will NOT create the namespace. Then, be sure that you are specifying a valid namespace.
 
 ```shell
 $ kubectl create namespace operator-test