If I was your client I'd be pissed that you decided to rewrite my code into a legacy version of Python. Make no mistake: Python 3 is the future of Python. There will be no version 2.8 and there is no going back to 2.7.
Also, I don't know what you mean by "Amazon only supports 2.7" because boto (the main client for Python) has supported Python 3 for 2 years now. Perhaps you mean Lambda?
+1. Also it's easy to write code that supports both, so if you really need python 2 support right now (surely AWS Lambda python 3 is coming soon, you can already use it unofficially) that's a much better option than being entrenched in python 2 (mainly the string handling is the issue for buggy code that'll run in 2 but not 3).
Also, I don't know what you mean by "Amazon only supports 2.7" because boto (the main client for Python) has supported Python 3 for 2 years now. Perhaps you mean Lambda?