How to upgrade AWS CLI to the latest version?

I recently noticed that I am running an old version of AWS CLI that is lacking some functionality I need:

$aws --versionaws-cli/1.2.9 Python/3.4.3 Linux/3.13.0-85-generic

How can I upgrade to the latest version of the AWS CLI (1.10.24)?

Edit:

Running the following command fails to update AWS CLI:

$ pip install --upgrade awscliRequirement already up-to-date: awscli in /usr/local/lib/python2.7/dist-packagesCleaning up...

Checking the version:

$ aws --versionaws-cli/1.2.9 Python/3.4.3 Linux/3.13.0-85-generic