When your application encounters an error, App Engine will shut down the request causing the error and return the following text to the user:
Error: Server Error The server encountered an error and could not complete your request. If the problem persists, please report your problem and mention this error message and the query that caused it.
The server error page will look similar to the following:
This error page is not the full error report; to see the actual error, you need to go to the Logs section of your App Engine application and find the error log. Here’s some pictures to help you find the error log:
First, go to your application dashboard and click the Logs link:
Click on the radio button marked Logs with minimum severity and choose Error from the dropdown box:
The logs page will automatically update to show all requests that failed.