code: sync files using FTP

My webhost doesn't support rsync, only FTP.  For grins I wrote a script to scan through interesting local files and push them up to my webhost.  Alas the progress wasn't as trivial as I'd hoped, so I abandoned the effort and used lftp the "mirror" command.

The code shows a number of best practices:

• don't store passwords/keys, pass them in via environment variables
• make an iterator of files, add to it using chain()
• Python3 subprocess.check_output() is a little odd
• logging, like voting, should be done early and often
• code ensures FTP connection always closed cleanly

https://github.com/shavenwarthog/johntellsall/blob/master/class/django-queryset/ftpsync.py