Confusing error when Artifactory URL returns a 404

[code-asher]

You get "file does not exist" which is confusing if you are doing something like adding an extension because it makes it sound like the vsix you are uploading does not exist.

The error should prepend the name of the thing that does not exist so something like "https://domain.com does not exist" or it should be entirely different: "https://domain.com returned a 404".

I believe the source of the problem is that we convert 404s into file not found errors to make Artifactory storage behave more like local storage but we should double-check what happens with other codes.