SFR-2249: Refactor and clean up s3 file process

[kylevillegas93]

Description

• Refactors and cleans up S3 file process
• Adds better error handling and logging
• Touch-up of the unit tests

Testing

make test; python main.py -p METProcess -e local -i complete -l 100; python main.py -p S3Process -e local

[mitri-slory]

This is a good way to refactor this process.

[Apophenia]

This looks great, I think the logging changes will be really helpful as well.