Fix bin scripts fo Python 3.

Fixes S3 and EC2 scripts so that they are valid Python 3. Some things may
still not work, but the scripts are now capable of running under Python 3.
This mostly involved updates to `print` statements.
Use sys.exit instead of raising SystemExit
Merge pull request #2502 from danielgtaylor/py3-bin

Fix bin scripts fo Python 3. Fixes #2502, #2490.