Improve responses from AWS to the consumer

[kirkbushell]

Feature Request

In Flysystem, if you do something like a exists() check, and your permissions are not configured correctly on AWS - what happens is that Flysystem gobbles up the exception provided by guzzle, providing an error message like:

Unable to check existence for: filename.png

This is not particularly helpful. The issue in my circumstance was that AWS was returning a 403 forbidden response. After doing some digging I realised that I could actually pull in the previous exception and see its message, so debugging was a breeze after that.

I think it might be better if Flysystem conveyed the message provided by the original exception. This would make debugging a lot easier. I'm not sure this is a standard across the library, but perhaps worth entertaining?

Scenario / Use-case

File operations against AWS.

Summary

Improve debugging capabilities through clearer error message reporting.