Does this deal with issue 583 or is this code path only used for Update Diff?
Show the File Not Found error when uploading diffs.
Review Request #1425 — Created Feb. 21, 2010 and submitted
Show the File Not Found error when uploading diffs. The Upload Diff dialog wasn't showing the File Not Found error. We were only showing form errors. Now we will show any error message we get, and have a mechanism for having the object we're working on provide us with a more detailed error message based on the returned data.
Tested it with a diff referencing a file that doesn't exist.