Python3: webob.Response.body must be bytes

Remove duplicate assignement for 'resp.body'. Use bytes in Python3.

Change-Id: Ice1beb997ae401ebb87762e5499970409c63d801
Python3: fix test_insecure

test_insecure() fails because it ends up calling guess_json_utf8() in the
requests module, where the count() method of the str type is called with bytes
input:

    nullcount = sample.count(_null)

This patch makes sure that we pass 'sample' as bytes.

Change-Id: I70071623d425ebbf910d3568a7b5c5d857892402
Python3: httpretty.last_request().body is now bytes

In Python 3, we must decode it before using it.

Change-Id: I473ba7b9732555ef5f9011a50d8684260e1f7f71
Merge "Python3: fix test_insecure"
Merge "Python3: webob.Response.body must be bytes"
Merge "Python3: httpretty.last_request().body is now bytes"