Add an alert in frontend when job cannot be submitted.

Test: Mannual tested.
Change-Id: I9076be48cf2efd8d545b88beb87ac0db651d39e4
diff --git a/tools/otagui/src/views/SimpleForm.vue b/tools/otagui/src/views/SimpleForm.vue
index 6d678a5..6ec1e74 100644
--- a/tools/otagui/src/views/SimpleForm.vue
+++ b/tools/otagui/src/views/SimpleForm.vue
@@ -170,6 +170,7 @@
         this.response_message = response.data
         alert(this.response_message)
       } catch (err) {
+        alert('Job cannot be started properly, please check.')
         console.log(err)
       }
       this.resetInput()