Fixes JSON error parsing error when receiving bytes in Python 3.

Should fix a couple errors:
https://github.com/boto/boto/issues/2681
https://github.com/boto/boto/issues/2677

That said, I had a bit of trouble with testing, so I'm not 100% on this... If you're going to try to test it, I suggest removing the try/except wrapping because I was getting a different TypeError in the testing framework than I was from the actual bug.