Improved error message when config file is not found

[steve-chavez]

Problem

Right now it shows:

postgrest: Fatal Error {fatalErrorMessage = "Error in config postgrest.conf: open File: does not exist (No such file or directory)"}

Because of the wrapping looks like users don't read it. See #3649.

Solution

Remove the Fatal Error wrapping.

As an extra, perhaps we can do a fuzzy search for all files under the current dir and provide a hint? (similar to how we suggest similar function names with RPC) If we don't have privileges then the hint will not show.