improve error messages for s3 sink errors

[miki725]

currently when s3 sink fails the only error message you get is 403: Permission Denied without too much information why it was denied. we should add a couple of common reasons why that might of happened as otherwise debugging IAM stuff is not fun:

• creds dont have access to the bucket in the uri
• if its MFA session, session token must be provided
• how to test local creds with vanilla aws cli