VSO azure deployment - Unable to retrieve connectiondetails

When deploying your application via visual studio online build process and using the "Azure App Service Deploy" build step, make sure the App Service you want to deploy to exists. Otherwise create it with the "Azure Resource Group Deployment" build step.

In this build step, you should have a template file for creating the App Service and the App Service Plan.

Otherwise the deployment will fail with the following error:

##[error]Webapp 'XXXNameXXX' doesn't exist. Webapp should exist before deployment.

This is a good error message and we know how to fix this.

BUT when deploying your application to a staging slot and the App Service doesn't exist you will get this error:

Not Found

Unable to retrieve connectiondetails for azureRM WebApp : Ews-TranslatorAPI. Status Code: 404 (Not Found)

Both messages mean the same: The App Service you are trying to deploy doesn't exists.