[bug 950358] Update raven-python from 3.1.16 to 3.6.1

This pull is a lot of changes, some of which are around the transform
method that serializes the environment to send to sentry which is where
we have a lot of problems.

It's hard to r? this short of saying, "yes--those two commits are in that repo." We'll have to test it on stage.

r?