Pedantry - there is no deletion or actual ‘move’ occurring, so refer to it as a copy operation. Move made me uncomfortable to run on a production system until I dug deeper to verify things weren’t going to delete everything on a live site.
Fix logging usage
Don’t hard-code the old storage backend as FileSystem, use the constant/variable defined above.
Only check if it exists once (for network / cloud based storage backend performance) and continue retrying if an SSLError is encountered (got running against Rackspace Cloud files)
Use same retry method to continue trying to copy the file to the new backend.