I recently noticed that I am running an old version of AWS CLI that is lacking some functionality I need:
$aws --version aws-cli/1.2.9 Python/3.4.3 Linux/3.1
On Mac you can use homebrew:
to install: brew install awscli
brew install awscli
to upgrade: brew upgrade awscli
brew upgrade awscli
Make sure you don't have multiple installations: where aws
where aws