How to upgrade AWS CLI to the latest version?

From http://docs.aws.amazon.com/cli/latest/userguide/installing.html#install-with-pip

To upgrade an existing AWS CLI installation, use the --upgrade option:

pip install --upgrade awscli

On Linux and MacOS X, here are the three commands that correspond to each step:

$ curl "https://s3.amazonaws.com/aws-cli/awscli-bundle.zip" -o "awscli-bundle.zip"
$ unzip awscli-bundle.zip
$ sudo ./awscli-bundle/install -i /usr/local/aws -b /usr/local/bin/aws