Builds started failing 7 days ago. Turns out it was because of the bump
from 1.4.28 to 1.4.29. It may not be worth playing whac-a-mole - I'll
file an issue in either the boto3 or botocore repo in the meantime.
botocore 1.3.29 (new as of yesterday) breaks a few of the s3 and
lambda tests; something about a StringIO being closed prematurely.
¯\_(ツ)_/¯
boto3 doesn't pin the botocore version; as a result the new version of
botocore gets pulled in transitively, breaking today's builds.
Signed-off-by: Scott Greene <scott.greene@getbraintree.com>