Requires redis-py 2.x

[breser]

Back in November 2018 redis-py updated to a 3.x version that has breaking changes to it, this tool is not compatible with redis-py 3.x. Noteable reasons why:

• It no longer coerces input into strings. Right now (at least with python 2.7) is passes unicode values to redis-py which causes it to throw an exception about unicode not having an iteritems method.
• ttl returns now match Redis' api and negative values imply that there is no ttl. If you dump with redis-py 3.x and then try to load with redis-py 2.x then your keys without ttls will be immediately deleted by redis because it'll set them to negative values rather than setting no ttl.

Tool still works fine if you just always use it with a compatible version or redis-py. I'd suggest adding some code to the tool to error out if you try to use it with a version it's not compatible with and a note in the README.md saying as much.

[p]

I see. As I do not presently use Python I'll leave this issue open for a potential contributor to address.