codes.py: fix input-with-completion on py3
codes.py: fix input-with-completion on py3

The input() function returns str(bytes) on py2, and str(unicode) on py3.
We want unicode in both cases.

warner/magic-wormhole,warner/magic-wormhole,warner/magic-wormhole,warner/magic-wormhole,david415/magic-wormhole