BUG - 500 Error Response from Initiate Upload when file exists has no error message

[joneubank]

Description

When attempting to use initializeMultipartUpload endpoint for a file that has already been uploaded, and the overwrite property is set to false, the request will end with an HTTP Error 500 and no explanation given for what failed.

Expected Behaviour

A descriptive error message explaining the cause of the failure.

Actual Behaviour

Generic 500 error response.

[joneubank]

The same error response occurs if the file is not found on the Metadata server.