how to debug error 500 Internal Server Error on an Azure App?

Question

I got an "500 Internal Server Error - An error occurred while starting the application" after deploying my application: https://iidapp.azurewebsites.net/

I keep finding the following error message but I am unable to find out on msdn websites any information describing how I can specify the SAS URL

INFO: The app was working for a long period and I didn't have to set the SAS URL; I wonder why suddenly Azure is generating exceptions

INFO2: the app works perfectly on my local machine

Any help is welcomed as I couldn't find any solution by reading the related topics on stackoverflow

2017-04-05T18:51:32
System.ApplicationException: The trace listener AzureBlobTraceListener is disabled. ---> System.InvalidOperationException: The SAS URL for the cloud storage account is not specified. Use the environment variable 'DIAGNOSTICS_AZUREBLOBCONTAINERSASURL' to define it.
   at Microsoft.WindowsAzure.WebSites.Diagnostics.AzureBlobTraceListener.RefreshConfig()
   --- End of inner exception stack trace ---

Answer 1

1. An error was triggered by W3SVC-WP : {app name}
   02000780
2. I found out on eventid that the code 02000780 meant that a file was missing
3. I eventually found out that it was possible to log further information by enabling the stdoulog inside the web.config . Read When a .NET Core Azure App Service won't start: 502.5 Process Failure
4. I opened the debug console and found out that a directory wasn't found https://{app_id}.scm.azurewebsites.net/DebugConsole

Voilà! I corrected the code and the app is up and running!