Description of changes:

Recent versions of Pylint added some new checks that recommend using syntax that was introduced in Python 3. This required two changes on our part:

1. The decrypt oracle is Python 3 only. There, I actually made the recommended changes (and re-enabled a similar check that was incorrectly disabled.)
2. Everywhere else, disable the new checks.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

Check any applicable:

• Were any files moved? Moving files changes their URL, which breaks all hyperlinks to the files.